PSY1105 Statistics PDF

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PSY1105 Stats Workshops

Get Started Open up Stata via Appstream (mq.okta.com) Type the following into the command line: webuse set https://s3-ap-southeast-2.amazonaws.com/mqpsychdata webuse tutors.dta

Descriptive Statistics Variable: Gender Bar chart Via menu: Graphics > Bar Chart > Graph of frequencies with categories > ‘Categories’ tab > tick Group 1 and select Gender as Grouping variable > Submit/OK Using syntax commands: graph bar (count), over (gender) Frequency table Via menu: Statistics > Summaries, tables, and tests > Frequency table > one-way > select Gender > Submit/OK Via syntax commands: tabulate gender

Variable: Age Histogram Via menu: Graphics > Histogram > select age > click frequency > Submit/OK Note: Default display for Y axis is Density – Select ‘frequency’ under ‘Y axis’ Via syntax commands: histogram age, freq Summary table Via menu: Statistics > Summaries, tables, and tests > Summary and descriptive statistics > Summary statistics > select age > choose what statistics you want displayed under ‘Options’ > Submit/OK Via syntax commands: summarize age

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PSY1105 Stats Workshops Practice time! For the variables listed below, what should you do for descriptive statistics? You need to think about whether they are numeric or categorical, and which graphic and numeric summaries are appropriate.    

Extraversion Neuroticism Openness to Experience Depression

Hypothesis Testing Variables: Gender and Conscientiousness Descriptive statistics Histogram within categories Via menu: Graphics > Histogram > select ‘consc’ under Variable drop-down menu > select frequency > go to ‘By’ tab > Tick ‘Draw subgraphs for unique values of variables’ and select ‘gender’ from drop-down menu under ‘Variables’ > Submit/OK Via syntax commands: histogram consc, frequency by(gender) Summary table Via menu: Statistics > Summaries, tables, tests > Summary and descriptive stats > Summary statistics > Enter consc > Go to ‘by/if/in’ tab > Tick ‘Repeat commands by groups’ box and select ‘gender’ from dropdown menu > Submit/OK Via syntax commands: by gender, sort : summarize consc

Checking assumptions Shapiro Wilk test within categories Via menu: Statistics > Summaries, tables, and tests > Distributional plots and tests > Shapiro-Wilk normality test > select ‘consc’ from drop-down menu under ‘Variables’ > go to ‘by/if/in’ tab > Tick ‘Repeat commands by groups’ box and select ‘gender’ from drop-down menu under ‘Variables that define groups’ > Submit/OK Via syntax commands: by gender, sort : swilk consc Levene’s test 2

PSY1105 Stats Workshops Via syntax commands: robvar consc, by(gender)

Independent samples t-test Via menu system: Statistics > summaries, tables and tests > Classical tests of hypotheses > t-test (mean comparison test) > select ‘Two-sample using groups’ > Select ‘consc’ under ‘Variable name’ > Select ‘gender’ under ‘Group variable name’ > Submit/OK Via syntax commands: ttest consc, by (gender)

Variables: Age and Agreeableness Descriptive statistics Same as earlier

Checking assumptions Shapiro Wilk test Via syntax: swilk age agree Scatterplot Via menu: Graphics > Twoway graph (scatter, line, etc.) > select ‘Create’ > select ‘Basic plot’ and ‘Scatter’ under ‘Choose a plot category and type > select ‘age’ for the x axis and ‘agree’ for the y axis under ‘Plot type’ > Accept > Submit/OK Via syntax commands: twoway scatter agree age twoway scatter agree age || lfit agree age

Correlation Via menu: Statistics > summaries, tables and tests > Summary and descriptive statistics > pairwise correlations > select ‘age’ and ‘agree’ using drop-down bar > select ‘Print number of observations for each entry’ > select ‘Print significance levels for each entry > Submit/OK Via syntax command: pwcorr age agree, obs sig

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PSY1105 Stats Workshops

Remember the Steps  What kind of variables do we have (and design)?  Univariate descriptive statistics  Which test is appropriate?  Null hypothesis and alternate hypothesis?  Run appropriate analysis (don’t forget to check assumptions)  Write Up + Conclusion

Practice time! 1. Are there any differences in (a) male and female extraversion (b) male and female neuroticism (c) male and female openness to experience? 2. Is there any difference between slow and fast readers’ (line) reaction time? Is there any difference between slow and fast readers’ (word) reaction time? 3. Is there a relationship between (a) openness and extraversion (b) trait anxiety and state anxiety (c) neuroticism and state anxiety 4. Is there a difference between line and word reaction time? (Note that all participants have both line and word reaction times!)

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