AP StatisticsName ______

4/4/05Coley / P. MyersPeriod ______

Quiz (Chapter 27)Honor Pledge ______

  1. Researchers want to determine whether training increases the capability of people to correctly predict outcomes of coin tosses. Each of twenty people is asked to predict the outcome (head or tails) of 100 independent tosses of a fair coin. After training, they are retested with a new set of 100 tosses. (All 40 sets of 100 tosses are independently generated.) Since the coin is fair, the probability of a correct guess is 0.5 on each toss. The numbers correct for each of the 20 people were as follows.

Score Before Training (number correct) / 46 / 48 / 50 / 54 / 54 / 54 / 54 / 54 / 54 / 54 / 55 / 56 / 57 / 58 / 58 / 61 / 61 / 63 / 64 / 65
Score After Training (number correct) / 61 / 62 / 53 / 46 / 50 / 52 / 53 / 59 / 60 / 61 / 55 / 59 / 55 / 50 / 56 / 58 / 64 / 57 / 61 / 54

Would knowing a person’s score before training be helpful in predicting his or her score after training? Justify your answer.

  1. A new process designed to increase the temperature inside steel girders shows great promise. In a test of 90 randomly selected girders, the following regression was performed; a partial computer printout is displayed:

PredictorCoeffStDevTP

Constant0.20740.23180.890.373

Temp 11.056510.02221??

S= 0.6009R-Sq = 96.3 %

Temp 1 is the initial temperature and Temp 2 is the temperature after the process has terminated.

(a)State the regression equation.

(b)Interpret the slope of the regression in the context of the problem.

(c)Interpret the value of R-Sq in words.

(d)Find the values of T and P indicated by the question marks in the printout.