Problem Set 2.7:Understanding Normal Distribution

Criterion:Solve problems with information about normal distributions and probabilities.

Instructions:Read the following and answer the questions.

Judging the humorousness of "lawyer" jokes.Stillman, Baumeister, and DeWall (2007) conducted a study where participants listened to a variety of jokes. To determine how funny the jokes were, the researchers asked a group of 86 undergraduates to rate the jokes on a scale from 1 (very unfunny) to 21 (very funny). Participants rated a "lawyer joke" as one of the funniest jokes, with a rating of 14.48 4.38 (MSD).

Assuming that these data are normally distributed,

1. What was the rating that marks the cutoff for the top 10% of participant ratings for this joke? X=20.08
2. The top 10% of scores is P=.1000 in the table C.1 so the Z score is Z=1.28.
3. 1.28= x14.48(M)
4. 4.38(SD)
5. Multiply 4.38 by 1.28 =5.60 14.48+5.60=20.08 So x=20.08
6. How many of the 86 undergraduates gave the joke a rating of at least 10?
7. 10-14.48/4.38= -1.0228using Z table .0885x86=7.611 move the decimal over one it would be 76.