Don’t drink the water!The movie A Civil Action (1998) tells the story of a

major legal battle that took place in the small town of Woburn, Massachusetts. A town well that supplied water to east Woburn residents was contaminated by industrial chemicals. During the period that residents drank water from this well, 16of 414babies born had birth defects. On the west side of Woburn, 3of 228babies born during the same time period had birth defects. Let p1be

the true proportion of all babies born with birth defects in west Woburn and p2be the true proportion of all babies born with birth defects in east Woburn. Check if the conditions for calculating a confidence interval forp1-p2are met.

Short Answer

Expert verified

It is not fit to find confidence interval forp1-p2

Step by step solution

01

Given Information

It is given that n1=414

x1=16

n2=228

x2=3

02

Explanation

Testing three conditions:

1. Random: As it is arbitrarily assigned, it is not met.

2. Independent: Due to used all values in population and not used sample, it is not satisfied.

3. Normal: There are only three success which is less than ten.

All conditions are not satisfied, it is not fit to find confidence intervalp1-p2

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Most popular questions from this chapter

A study of road rage asked separate random samples of 596men and 523 women

about their behavior while driving. Based on their answers, each respondent was

assigned a road rage score on a scale of 0 to 20. Are the conditions for performing a

two-sample t test satisfied?

a. Maybe; we have independent random samples, but we should look at the data to

check Normality.

b. No; road rage scores on a scale from 0 to 20 can’t be Normal.

c. No; we don’t know the population standard deviations.

d. Yes; the large sample sizes guarantee that the corresponding population

distributions will be Normal.

e. Yes; we have two independent random samples and large sample sizes.

Candles A company produces candles. Machine 1 makes candles with a mean

length of 15cm and a standard deviation of 0.15cm. Machine 2 makes candles with a

mean length of 15cm and a standard deviation of 0.10cm. A random sample of 49

candles is taken from each machine. Let x ̄1−x ̄2 be the

difference (Machine 1 – Machine 2) in the sample mean length of candles. Describe the

shape, center, and variability of the sampling distribution of x ̄1−x ̄2.

The P-value for the stated hypotheses is 0.002Interpret this value in the context of this study.

a. Assuming that the true mean road rage score is the same for males and females, there is a 0.002probability of getting a difference in sample means equal to the one observed in this study.

b. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

c. Assuming that the true mean road rage score is different for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

d. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the null hypothesis is true.

e. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the alternative hypothesis is true.

Music and memory Refer to Exercise 87.

a. Construct and interpret a 99%confidence interval for the true mean difference. If you already defined the parameter and checked conditions in Exercise87, you don’t need to do them again here.

b. Explain how the confidence interval provides more information than the test in Exercise .

Thirty-five people from a random sample of 125 workers from Company A admitted

to using sick leave when they weren’t really ill. Seventeen employees from a random

sample of 68 workers from Company B admitted that they had used sick leave when

they weren’t ill. Which of the following is a 95% confidence interval for the difference

in the proportions of workers at the two companies who would admit to using sick

leave when they weren’t ill?

(a) 0.03±(0.28)(0.72)125+(0.25)(0.75)68

(b) 0.03±1.96(0.28)(0.72)125+(0.25)(0.75)68

(c) 0.03±1.645(0.28)(0.72)125+(0.25)(0.75)68

(d) 0.03±1.96(0.269)(0.731)125+(0.269)(0.731)68

(e)0.03±1.645(0.269)(0.731)125+(0.269)(0.731)68

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