Statistics Question

Stroop Test1
Title
HAFSA KHAN
PSYCHOLOGY DEPARTMENT, NORTHEASTERN UNIVERSITY
Abstract
The purpose of the experiment was to determine whether the time to determine the color of a
word is slower when the letters spell a different color, compared to when the color and word are
the same. Our study showed that Stroop Effect was significant and the mean reaction time, when
color and word were the same, was significantly lower than the mean reaction time when color
and word were different. In other words, the time to determine the color of a word is indeed
slower when the letters spell a different color, compared to when the color and word are the
same. Another purpose of the study was to determine whether asking participants to imagine that
the letters on the screen are meaningless symbols can reduce the Stroop Effect. Our study
showed that the magnitude of the Stroop effect for the group receiving ‘suggestion’ instructions
Stroop Test
2
was significantly smaller than the magnitude of the Stroop effect for the group receiving regular
instructions. However, our study showed that meaningless symbols cannot significantly reduce
the Stroop Effect, and asking the participants to imagine that the letters on the screen are
meaningless symbols cannot significantly reduce the Stroop Effect.
Introduction
The Stroop effect is a psychological phenomenon described as our tendency to experience
difficulty naming a physical color when it is used to spell the name of a different color. This
effect was first described in the 1930s by psychologist John Ridley Stroop. The following study
was a partial replication of two previous studies, one by Stroop (1935) and the other by Raz et al.
(2006).
A hypothesis test was performed to determine whether reaction time is faster when the color and
word are the same compared to when they are different (i.e., a test for the Stroop Effect). A
second hypothesis test was performed to determine whether the Stroop Effect (increased reaction
time when color and word are different) is smaller when participants are asked to imagine that
the letters are meaningless symbols. A third hypothesis test was performed to compare the
magnitude of the Stroop effect for “suggestion” instructions versus regular instructions. A fourth
hypothesis test was performed for comparing the magnitude of the Stroop effect for respondents
whose first language was English and for those whose first language was not English
Method
Participants
The participants of this study were 31 students from three sections of the senior-level research
methods and statistics course (2 nonbinary, 22 female, and 7 male). The students participated in
Stroop Test
3
the experiment as part of a class project. Participants ranged in age from X to X (M = XX.X, SD
= X.XX).
Materials
The materials needed to complete this Qualtrics survey were; access to the internet/wifi,
computer/laptop, the survey link, the experiment link, working keyboard.
Procedure
For this study, everyone was to take a survey online called the Qualtrics Survey. Each student
had to answer a couple of questions such as; age, gender, class section, etc… once you answer
these questions you click to move forward and are given a list of instructions. There are two sets
of instructions you can get in the survey it is randomized so you won’t know which one you or a
classmate has gotten. The objective of this study is to correctly identify the color the word is
written in, not the color in which the word is spelled. For instruction number one the rule that is
given is to imagine that the letters are meaningless symbols Your job is to decide what color the
meaningless symbols are. If they are red press the “r” key as fast as you can. If they’re blue press
“b”, if they’re green press “g” and if they’re yellow press “y”. The group who got the second
instruction was told Your job is to decide what color the letters are. If they are red press SHORT
TITLE 4 with the “r” key as fast as you can. If they’re blue press “b”, if they’re green press “g”
and if they’re yellow press “y”. Once you get your instructions you click on the survey link
which opens a new tab, are not close the survey tab, because you will need to come back to it
after you finish your trails. When all the trials are done you had to click the view results button
and scroll down to where it says “ average time for different color/word” and “ average time for
same color/word. You take the results and submit them back into your survey. Once everything is
filled out you can submit the survey and exit the tabs.
Stroop Test
4
Results
A paired t-test was performed for testing the presence of the Stroop Effect, i.e., the discrepancy
in reaction time. The paired t-test tested whether the mean reaction time when color and word
were the same was smaller as compared to the mean reaction time when color and word were
different.
Table 1. Paired samples T-Test Results for Presence of Stroop Effect
statistic df
Same
Different
Student’s t
-2.91
Cohen’s d
-0.523
p
Effect Size
30.0
0.003
Note. Hₐ μ Measure 1 – Measure 2 < 0 Table 2. Descriptive Statistics for Presence of Stroop Effect N Different Same 31 31 3034 2502 1385 1206 Mean Median SD 4652 3783 SE 835 679 The mean reaction time when color and word were the same (M = 2502, SD = 3783) was significantly smaller as compared to the mean reaction time when color and word were different (M = 3034, SD = 4652); t (df = 30) = -2.91, p-value = 0.003. The effect size was medium with Cohen’s d = -0.523. An independent samples t-test was performed for comparing the magnitude of the Stroop effect for regular instructions versus “suggestion” instructions. Levene's test was significant (p < .05), suggesting a violation of the assumption of equal variances for the two groups of the independent variable. Hence an independent samples t-test, assuming unequal variances, was performed to test whether the magnitude of the Stroop effect for the group receiving ‘suggestion’ Stroop Test 5 instructions was smaller than the magnitude of the Stroop effect for the group receiving regular instructions. Table 3. Independent Samples T Test Results (IV: Group, DV: Stroop Effect) Statistic df p ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Note. Hₐ μ suggestion instructions < μ regular instructions Stroop Effect Student's t -2.43 ᵃ 29.0 0.011 Median SD Table 4. Descriptive Statistics (IV: Group, DV: Stroop Effect) Group Stroop Effect N Mean SE suggestion instructions 18 182 148 250 59.0 regular instructions 13 1016 315 1437 399 The magnitude of Stroop effect for the group receiving ‘suggestion’ instructions (M = 182, SD = 250) was significantly lower than the magnitude of Stroop effect for the group receiving regular instructions (M = 1016, SD = 1437); t (df = 29) = -2.43, p-value = 0.011. The effect size was large with Cohen’s d = -0.883. An independent samples t-test was performed to determine whether asking participants to imagine that the letters on the screen are meaningless symbols can reduce the Stroop Effect. Table 5. Independent Samples T Test Results (IV: Check, DV: Stroop Effect) Stroop Effect Student's t Statistic df p -1.43 ᵃ 29.0 0.082 Effect Size Cohen's d -0.535 Stroop Test 6 Note. Hₐ μ meaningless symbols < μ letters ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Table 6. Descriptive Statistics (IV: Check, DV: Stroop Effect) Group Stroop Effect N Mean Median SD SE meaningless symbols 11 186 196 174 52.5 letters 20 722 304 1230 275 There was no significant difference in the magnitude of Stroop effect for letters (M = 722, SD = 1230) and meaningless symbols (M = 186, SD = 174); t (df = 29) = -1.43, p-value = 0.082. The effect size was small with Cohen’s d = -0.535. An independent samples t-test was performed for comparing the magnitude of the Stroop effect for respondents whose first language was English and for those whose first language was not English (1 = Yes, 2 = No). Levene's test was significant (p < .05), suggesting a violation of the assumption of equal variances for the two groups of the independent variable. Table 7. Independent Samples T Test Results (IV: English, DV: Stroop Effect) Stroop Effect Student's t Statistic df p 1.29 ᵃ 29.0 0.208 Effect Size Cohen's d 0.495 ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Table 8. Descriptive Statistics (IV: English, DV: Stroop Effect) Stroop Test 7 Group Stroop Effect N Mean Median SD SE yes 21 693 223 1205 263 no 10 194 213 201 63.6 There was no significant difference in the magnitude of Stroop effect for the respondents whose first language was English (M = 223, SD = 1205) and for those whose first language was not English (M = 194, SD = 201); t (df = 29) = 1.29, p-value = 0.208. The effect size was small with Cohen’s d = 0.495. Discussion Our study showed that Stroop Effect was significant. The hypothesis was that the mean reaction time, when color and word were the same, was significantly lower than the mean reaction time when color and word were different. The hypothesis was supported by the results, and it was found that the time to determine the color of a word is indeed slower when the letters spell a different color, compared to when the color and word are the same. The result was consistent with previous research by Stroop in 1935, where he found that “the interference of conflicting word stimuli upon the time for naming 100 colors (each color being the print of a word which names another color) caused an increase of 47.0 seconds or 74.3% of the normal time for naming colors printed in squares.” (Stroop, 1935). Our findings were also consistent with the findings of the study by Elliott in 2015, where he showed that people tend to be faster at identifying the font color when the word name and font color are the same and slower when they are different. (Elliott, 2015). “Two factors underlie Stroop interference: dimensional imbalance and dimensional uncertainty. Dimensional imbalance reflects how correlated the two dimensions of a Stroop Test 8 stimulus are and how surprising a stimulus is and determines the ease of recovery of a stimulus representation from memory. Dimensional uncertainty reflects how salient a stimulus is, notably how likely or unlikely it is in the context of other (recently presented) stimuli.” (C. M. MacLeod, 2015). Our study showed that the magnitude of the Stroop effect for the group receiving ‘suggestion’ instructions was significantly smaller than the magnitude of the Stroop effect for the group receiving regular instructions. This result was also consistent with previous research by Raz et al in 2006, where the researchers had examined the effects of suggestion on Stroop interference in highly suggestible individuals, where participants had completed the Stroop task with and without a suggestion to perceive Stroop words as meaningless symbols. “Suggestion produced a significant reduction in Stroop inhibition, accounting for about 45% of the variance in Stroop responding, regardless of whether hypnosis had been induced. These findings indicate that suggestion can at least partially overcome the automaticity associated with the Stroop effect”. (Raz et al., 2006). However, our study showed that meaningless symbols cannot significantly reduce the Stroop Effect, and asking the participants to imagine that the letters on the screen are meaningless symbols cannot significantly reduce the Stroop Effect. This result did not support our hypothesis and was not consistent with previous research by Raz et al in 2006. (Raz et al., 2006). This might be owing to the small sample size considered in our study. Our study also showed that there was no significant difference in the magnitude of the Stroop effect for the respondents whose first language was English than those whose first language was not English. Stroop Test 9 References Elliott, Charles. (2015). The Stroop Effect on Color and Word Identification. MacLeod, Colin M. (2015). The Stroop Effect. Encyclopedia of Color Science and Technology DOI 10.1007/978-3-642-27851-8_67-1. Springer Science + Business Media New York 2015 Raz, A., Kirsch, I., Pollard, J., & Nitkin-Kaner, Y. (2006). Suggestion reduces the Stroop effect. Psychological Science, 17(2), 91-95. https://doi.org/10.1111/j.1467-9280.2006.01669.x Stroop Test 10 Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643-662. https://doi.org/10.1037/h0054651 Checklist for SRM II Paper Assignment – Fall 2022 Below are the sections required for the assignment and the key elements of each section Overall Format – 1st Submission  Manuscript follows APA Style (7th Edition); Use APA permitted font (recommended Times New Roman 12 pt)  Margins need to all be 1”  Page header should be identical for all pages of manuscript  To start a new page, insert a page break by pressing Ctrl-Enter, not by repeatedly pressing Enter until you get to a new page (this will cause later formatting problems) Title Page – 1st Submission  Page header needs to be in APA format (and include short title)  Manuscript title, name, and departmental/institutional affiliation need to be in APA format (Professional Paper)  Title needs to be relevant to study Abstract – 3rd Submission (have designated page with section header in 1st Submission)  Needs to be in APA format (no indent to first line!)  Maximum 250 words (per APA guidelines – see Abstract & Keywords guide here)  Includes: relevant background information, basics of study method, major findings, and major conclusions Introduction – 3rd Submission (have designated section header only in 1st submission)  Title and section need to be in APA format  Need to present information from and cite Stroop (1935) and Raz et al. (2006) articles and minimum of two additional peer-reviewed empirical articles relevant to study hypotheses (the required papers + 2 additional papers are available in Unit 6 on D2L)  Bonus credit (½ point) can be earned for each additional reference incorporated after 4 cited (2 points maximum)  Need to present background information relevant to the key aspects of study: Stroop effect & evidence, effect of suggestion on Stroop effect  Need to define and describe key terms (e.g., what does Stroop effect mean?)  Needs to be organized thematically, not as a series of summaries of prior research studies  Section needs to end with a paragraph setting up the current study – noting in what ways study replicates or is testing hypotheses from prior research, how it is different, stating research hypotheses or questions, etc. Method – 1st Submission  Section begins immediately following Introduction (no page break)  Section header and section subheadings need to be in APA format  Method needs to be written in past tense (study is now complete)  Participants: include sample size, description of important characteristics (depending on characteristic may be frequencies, mean, standard deviation, range, etc.), how participants were recruited to be in the study  Materials: describe the survey used in the current study (see PDF posted on D2L) – avoid block quoting, paraphrase instead, do not include survey in an appendix  Procedure: describe the steps that were followed to conduct the experiment & collect the data Results – 2nd Submission (have designated section header only in 1st submission)  Section begins immediately following Method (no page break)  Section header needs to be in APA format  Mandatory analysis 1: paired t-test comparing reaction time for when color & word are the same versus different (you are testing for the presence of the Stroop Effect, i.e., the discrepancy in reaction time)  Mandatory analysis 2: independent t-test comparing size of Stroop effect for regular instructions vs. “suggestion” instructions  Mandatory analysis 3: one additional independent t-test of your choice, related to the topic of the study  You can get extra credit (1 point per analysis) for additional analyses if they are meaningful, relevant, and summarized appropriately, plus accompanied by a Table or Figure (2 points maximum extra credit)  Each finding should be fully reported in proper APA format with all relevant information  You must refer to a Table or Figure for EACH result that you present (recommendation: for t-tests use Figures!)  Findings should be presented in separate paragraphs unless closely linked (e.g., same independent variable)  Format each result as follows: describe what you tested & how, refer to either a Figure or Table, then summarize your findings (statistical test in APA format, give descriptive stats – M and SD if you have a Figure)  Avoid repeating the exact same sentence structure in writing up each result Discussion – 3rd Submission Outline Only; 4th Submission completed (section header only in 1 st/2nd submissions)  Section begins immediately following Results (no page break)  Section header needs to be in APA format  Summarize in words and then discuss each major finding (DO NOT report statistics here!)  Discuss each finding/group of related findings separately – only discuss issues relevant to that finding (i.e., was the hypothesis supported? Is it consistent or inconsistent with previous research? Why do you think we got the finding that we did?)  When you are discussing a result that was also tested in research that you cited in the Introduction, you need to clearly compare your result and cite the original study – note if you obtained similar or different findings  Have a separate paragraph at the end about “Limitations & Directions for Future Research” where you talk about general methodological limitations to the study overall and how you would address these in future studies References – 3rd Submission (have designated page with section header in 1st Submission)  Section begins on a new page following Discussion  References need to be reported in proper APA format  You must include all references cited (and no extras!)  You must include the required Stroop (1935) and Raz et al. (2006) papers and at least 2 additional references  To get extra credit for extra references, they MUST be included in the 3rd submission, and they must be discussed in some detail in the Introduction and/or Discussion sections Tables (Optional) – 2nd Submission (and all subsequent submissions)  Tables need to be numbered in the order in which they are referenced in the Results section  Each Table goes on a separate page  Table number and Table title need to be in proper APA format  The body of the Table (including borders, headers, and content) needs to be in proper APA format  If Tables are included, all Tables need to be placed before Figures; numbering starts at “1” for Tables and Figures Figures – 2nd Submission (and all subsequent submissions)  A minimum of two Figures is required, and you must have either a Figure or a Table (not both!) for each analysis  Figures need to be numbered in the order in which they are referenced in the Results section  Each Figure goes on a separate page  Figure number and figure caption need to be in proper APA format General Writing Style – ALL Submissions  Manuscript needs to be written in past tense  Avoid use of first or second person pronouns (i.e., I, we, you)  Avoid language that is too informal or colloquial (such as slang)  Do not use contractions  Remember that even in the more technical sections (such as Method and Results), your sections still need to read as a narrative – you need to have complete sentences that are grammatically correct  Remember that you can earn up to 2 points of extra credit for additional references and/or additional analyses Figure 1 Mean Reaction: Stroop Effect. Figure 2 Mean Stroop Effect: Instructions on Stroop Effect. Figure 3 Mean Stroop Effect: English first language (yes or no) on Stroop Effect. SHORT TITLE 1 Match the right ink color Hafsa Khan Psychology Department, Northeastern University Stats & Research Method II Nadia Silverthorn October 12, 2022 SHORT TITLE 2 Abstract Introduction Method Participants The participants of this study were college students in SRM II. There are three sections of the SRM II class. You could be a participant from either of the three sections; MW 11:30, MW 5:40, or TR 1:40. From the three sections there was a total of 31 participants. Which consisted of 2 nonbinary, 22 females, and 7 males. Materials The materials you need to complete this Qualtrics survey are; access to the internet/wifi, computer/laptop, the survey link, the experiment link, working keyboard. Procedure For this study, everyone was to take a survey online called the Qualtrics Survey. Each student had to answer a couple of questions such as; age, gender, class section, etc… once you answer these questions you click to move forward and are given a list of instructions. There are two sets of instructions you can get in the survey it is randomized so you won’t know which one you or a classmate has gotten. The objective of this study is to correctly identify the color the word is written in, not the color in which the word is spelled. For instruction number one the rule that is given is to imagine that the letters are meaningless symbols Your job is to decide what color the meaningless symbols are. If they are red press the “r” key as fast as you can. If they’re blue press “b”, if they’re green press “g” and if they’re yellow press “y”. The group who got the second instruction was told Your job is to decide what color the letters are. If they are red press the “r” key as fast as you can. If they’re blue press “b”, if they’re green press “g” and if they’re yellow press “y”. Once you get your instructions you click on the survey link which opens a new tab, are not close the survey tab, because you will need to come back to it after you finish your SHORT TITLE 3 trails. When all the trials are done you had to click the view results button and scroll down to where it says “ average time for different color/word” and “ average time for same color/word. You take the results and submit them back into your survey. Once everything is filled out you can submit the survey and exit the tabs. Results Paired Samples T-Test Differen t Same Student's t statistic df p Effect Size 2.91 30. 0 0.00 3 Cohen's d 0.523 Note. Hₐ μ Measure 1 - Measure 2 > 0
Descriptives
N
Mean
Median
SD
SE
Differen
t
3
1
3034
1385
465
2
83
5
Same
3
1
2502
1206
378
3
67
9
Statistic
df
p
-2.43 ᵃ
29.0
0.011
^ 1. test for Stroop effect (1-tailed)
Independent Samples T-Test
StroopEffect
Student’s t
Effect Size
Cohen’s d
Note. Hₐ μ suggestion instructions < μ regular instructions ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances -0.883 SHORT TITLE 4 Group Descriptives Group StroopEffec t N Mean Median SD SE 1 8 182 148 250 59. 0 1 3 1016 315 143 7 399 suggestion instructions regular instructions 2 test effect of experimental instructions - Independent t IV: group DV: Stroop effect (1-tailed) Independent Samples T-Test StroopEffect Statistic df p 1.29 ᵃ 29.0 0.208 Student's t Effect Size Cohen's d ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Group Descriptives Group StroopEffec t yes no N Mean Median SD SE 2 1 693 223 120 5 263 1 0 194 213 201 63. 6 0.495 SHORT TITLE 5 3 IV: English ID: Strrop effect Independent Samples T-Test Same Student's t Statistic df p Effect Size 1.16 ᵃ 28.0 0.257 Cohen's d 0.438 ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Group Descriptives Group Same under 25 25 and older N Mean Median SD SE 1 9 3160 1235 471 3 108 1 1 1 1486 1170 909 274 3 IV: Age group DV: same Independent Samples T-Test Different Student's t Same Student's t Statistic df p 1.07 ᵃ 28.0 0.293 1.16 ᵃ 28.0 0.257 Effect Size Cohen's d Cohen's d 0.406 0.438 SHORT TITLE 6 ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances Group Descriptives Group Differen t under 25 25 and older Same under 25 25 and older N Mean Median SD SE 1 9 3784 1510 579 2 132 9 1 1 1871 1368 132 3 399 1 9 3160 1235 471 3 108 1 1 1 1486 1170 909 274 Statistic df p 1.07 ᵃ 28.0 0.293 3 DV: differnt & same IV: Age group Independent Samples T-Test Different Student's t Effect Size Cohen's d ᵃ Levene's test is significant (p < .05), suggesting a violation of the assumption of equal variances 0.406 SHORT TITLE 7 Group Descriptives Group Differen t N Mean Median SD SE 1 9 3784 1510 579 2 132 9 1 1 1871 1368 132 3 399 under 25 25 and older 3 IV: Age group DV: different Discussion Reference Table(s) (optional) Figure (s)