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The Department of Psychology

The Department of Psychology. presents Dr. Christopher Ferguson Do Angry Birds Make For Angry Children? How Psychological Science Got Video Game Effects Wrong 4:00 p.m. Monday, December 9th 1011 Bartley Hall. Seven Steps for Doing  2. 1) State the hypothesis 2) Create data table

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The Department of Psychology

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  1. The Department of Psychology presents Dr. Christopher Ferguson Do Angry Birds Make For Angry Children? How Psychological Science Got Video Game Effects Wrong 4:00 p.m. Monday, December 9th 1011 Bartley Hall

  2. Seven Steps for Doing 2 • 1) State the hypothesis • 2) Create data table • 3) Find 2 critical • 4) Calculate the expected frequencies • 5) Calculate 2 • 6) Decision • 7) Put answer into words

  3. Example • With whom do you find it easiest to make friends? • Subjects were either male and female. • Possible responses were: “opposite sex”, “same sex”, or “no difference” • Is there a significant (.05) relationship between the gender of the subject and their response?

  4. Results

  5. Step 1: State the Hypothesis • H1: There is a relationship between gender and with whom a person finds it easiest to make friends • H0:Gender and with whom a person finds it easiest to make friends are independent of each other

  6. Step 2: Create the Data Table Add “total” columns and rows

  7. Step 3: Find 2 critical • df = (R - 1)(C - 1) • df = (2 - 1)(3 - 1) = 2 •  = .05 • 2 critical = 5.99

  8. Step 4: Calculate the Expected Frequencies

  9. Step 5: Calculate 2 O = observed frequency E = expected frequency

  10. 2

  11. 2

  12. 2

  13. 2

  14. 8.5 2

  15. Step 6: Decision • Thus, if 2 > than 2critical • Reject H0, and accept H1 • If 2 < or = to 2critical • Fail to reject H0

  16. 2 = 8.5 2 crit = 5.99 Step 6: Decision • Thus, if 2 > than 2critical • Reject H0, and accept H1 • If 2 < or = to 2critical • Fail to reject H0

  17. Step 7: Put answer into words • H1: There is a relationship between gender and with whom a person finds it easiest to make friends • A persons gender is significantly (.05) related with whom it is easiest to make friends.

  18. Practice • Is there a significant ( = .01) relationship between opinions about the death penalty and opinions about the legalization of marijuana? • 933 Subjects responded yes or no to: • “Do you favor the death penalty for persons convicted of murder?” • “Do you think the use of marijuana should be made legal?”

  19. Results Marijuana ? Death Penalty ?

  20. Step 1: State the Hypothesis • H1: There is a relationship between opinions about the death penalty and the legalization of marijuana • H0:Opinions about the death penalty and the legalization of marijuana are independent of each other

  21. Step 2: Create the Data Table Marijuana ? Death Penalty ?

  22. Step 3: Find 2 critical • df = (R - 1)(C - 1) • df = (2 - 1)(2 - 1) = 1 •  = .01 • 2 critical = 6.64

  23. Step 4: Calculate the Expected Frequencies Marijuana ? Death Penalty ?

  24. Step 5: Calculate 2

  25. Step 6: Decision • Thus, if 2 > than 2critical • Reject H0, and accept H1 • If 2 < or = to 2critical • Fail to reject H0

  26. 2 = 3.91 2 crit = 6.64 Step 6: Decision • Thus, if 2 > than 2critical • Reject H0, and accept H1 • If 2 < or = to 2critical • Fail to reject H0

  27. Step 7: Put answer into words • H0:Opinions about the death penalty and the legalization of marijuana are independent of each other • A persons opinion about the death penalty is not significantly (.01) related with their opinion about the legalization of marijuana

  28. Sam Sleepresearcher hypothesizes that people who are allowed to sleep for only four hours will score significantly lower than people who are allowed to sleep for eight hours on a cognitive skills test. He brings sixteen participants into his sleep lab and randomly assigns them to one of two groups. In one group he has participants sleep for eight hours and in the other group he has them sleep for four. The next morning he administers the SCAT (Sam's Cognitive Ability Test) to all participants. (Scores on the SCAT range from 1-9 with high scores representing better performance). Was Sam correct?

  29. Indepdent t-test (2 sample with equal n) t obs = .847 t crit (one tailed) = 1.76 Sam's hypothesis was not confirmed. He did not find a significant difference between those who slept for four hours versus those who slept for eight hours on cognitive test performance.

  30. Before making their recommendations, administrators in a large urban district take a random sample of 50 seventh graders and compare the achievement levels of those who attended pre-school and those who did not. If achievement is independent of attending pre-school then the proportions at each level should be equal. Determine if there is an association between attending preschool and algebra achievement.

  31. Chi-square = 2.85 • Chi-square crit = 5.99 • Achievement is unrelated to whether or not a child attended preschool.

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