Psychology Statistics

EXAM3 – Review Questions from Previous Exams

1.  Jessie  thinks  that  people  eat  more  chocolate  when  they’re  in  a  bad  mood.    Jessie  knows  that   people generally eat an average of 4.1 chocolate bars per month and that the number of chocolate bars people eat per month is normally distributed. Therefore, to test her theory, she selects 25 people who report that they have been in a bad mood for the past year and finds that these 25 people ate an average of 4.4 chocolate bars per month, standard deviation 0.5. Is Jessie right? (9)

2. (10 marks) Monica believes that people who meditate live happier lives. To test her theory, Monica asks people to rate their happiness on a scale from 1-10. She uses a sample of 6 people  who  don’t   meditate and another sample of 6 people  who  meditate  regularly.    Is  Monica’s  theory  correct?                           SSno meditation = 10, SSmeditation = 10.83

No

meditation

Meditation

4 8

6 7

7 5

5 8

3 6

5 9

3.  (3  marks)  Antonia  also  thinks  that  meditation  will  change  happiness  levels,  but  she’s  not  sure  in  which   direction the change will occur. So, Antonia decides to use a different design and tests 5 people before and after undergoing a meditation regimen. The data follows. Construct the 95% Confidence Interval for the average change in happiness ratings (Note: you do not have to conduct a t-test, you just have to construct the confidence interval). The estimated standard error of the difference is 0.86.

Before After

3 5

5 6

6 4

4 7

5 5

BONUS: Explain the meaning of what you just calculated in one sentence.

BONUS: If you had conducted a t-test, would you have rejected or failed to reject the null?

BONUS: If Antonia had used a larger sample, would her confidence interval be narrower (i.e., smaller) or wider (i.e., larger)?

4.  (12  marks)  Julian  wants  to  know  if  playing  an  instrument  affects  people’s  hearing.    So,  he  recruits  5   piano players, 5 flute players and 5 percussionists and tests them all to see how many words they can hear in a noisy environment. The data follows. Is there evidence that the type of instrument one plays affects  a  person’s  hearing?

Piano Flute Percussion

10 5 4 6 7 8 8 9 3 5 8 10 11 6 5 T = 40 T = 35 T = 30 s = 2.55 s = 1.58 s = 2.92

BONUS: If Julian only compared piano players and flute players (i.e., two groups only), what would have been his decision for the corresponding t-test?