Opgaven bijeenkomst 4 - Statistiek voor HMI

1. Twenty-five women between the ages of 70 and 80 were randomly selected from the general population of women their age to take part in a specia1 program to decrease (speed) reaction time. After the course, the women had an average reaction time of 1.5 seconds. Assume that the mean reaction time for the general population of women of this age group is 1.8, with a standard deviation of .5 seconds. (Also assume that the population is approximately normal.) What should you conclude about the effectiveness of the course? (a) Carry out the steps of hypothesis testing (use the .01 level). (b) Figure the 99% confidence interval.

2. In each of the following studies, a single sample's mean is being compared to a population with a known mean but an unknown variance. For each study, decide whether the result is significant.

3. A program to decrease littering was carried out in four cities in California’s Central Valley starting in August 2001. The amount of litter in the streets (average pounds of litter collected per block per day) was measured during the July before the program started and then the next July, after the program had been in effect for a year. The results were as follows:

Using the 1% level of significance, was there a significant decrease in amount amount of litter? 4. A study was done of personality characteristics of 100 students who were tested at the beginning and end of their first year of college. The researchers reported the results in the following table:

SD (=S): unbiased estimate of population standard deviation.

a. Wich test is suitable to investigate id\f the differences in (for example) Anxiety between Fall and Spring are significant? b. The mean of Anxiety is marked with **. What does this mean? c. Explain how this (for example ** for the M of Anxiety) is found. Calculate the t- value for this example.