Stat 366 Lab 12 Problems (November 30, 2006) page 1
Large-Sample Hypothesis Testing
10.8 The hourly wages in a particular industry are normally distributed with mean $13.20 and
standard deviation $2.50. A company in this industry employs 40 workers, paying them an
average of $12.20 per hour. Can this company be accused of paying substandard wages? Use
an α=.01 level test.
10.11 Shear strength measurements derived from uncounted compression tests for two types of soils
gave the results shown in the following table (measurements in tons per square foot).
Soil Type I Soil Type II
n1= 30 n2= 35
¯y1= 1.65 ¯y2= 1.43
s1= 0.26 s2= 0.22
Do the soils appear to differ with respect to average shear strength, at 1% significance level?
10.15 According to a New York Times/CBS News poll (Gainesville Sun, November 3, 1994), 60%
of the 1429 adults interviewed were unable to name an elected official whom they admired.
Is there sufficient evidence to claim that a majority of adults are unable to name an elected
official whom they admire? Use a .01 level test.
10.17 A survey conducted by the National Association of College Admission Counselors examined
enrollment in colleges and universities for the years 1991 and 1992 (USA Today, August 18,
1992). The 1992 survey was based on 1323 questionnaires; we will assume that the number
of responses in 1991 was 1225. The 1992 results indicated that 71% of the colleges reported
an increase in applications, compared with 50% in 1991. Do the data indicate a significant
difference in the proportions of colleges reporting an increase in applications for the years
1991 and 1992? Use α=.01.