Homework Answers

1.     In a survey of 1500 households, it is found that 47% of them have a high-definition television (based on data from the consumer electronics association). Use a 0.01 significance level to test the claim that fewer than half of all households have a high definition television.  Are the results from a few years ago likely to be valid today?

A cement manufacturer claims that the average weight of his product is 40 kg: with a standard deviation of 2.35 kg A sample of 45 bags was taken and found to have a mean weight of 38.71 kg: Are we going to accept the claim of the cement manufacturer? Use 0.01 level of significance

1.     In a Harris poll of 630 human resource professionals, 38.4 % said that they had at least one child by the age of 30 years.

a. Among the 630 professionals who were surveyed, how many of them said they had at least one child before 30 years of age.

b. Construct a 99% confidence interval estimate for the proportion of all human resource professionals with at least one child before 30 years of age.

c. Repeat part (b) using a confidence interval level of 90%.

d. Compare the confidence intervals from part (b) and (c) and identify the interval that is wider. Why is it wider?

1.     A particular brand of petrol was used in 80 randomly chosen cars of the same model and age. The petrol consumption, x miles per gallon, was obtained for each car. The results are summarized by

∑x=1896 and ∑x²=45959.

Calculate a 99% confidence interval for the mean petrol consumption of all cars of this model and age.