The IQ scores for a random sample of subjects with low lead levels in their blood and another random sample of subjects with high lead levels in their blood were collected. The statistics are summarized in the accompanying table. Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. Complete parts (a) to (c).

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Part 1

		mu	n	x overbarx	s
Low Lead LevelLowLeadLevel	mu 11	7171	90.5076990.50769	15.2736915.27369
High Lead LevelHighLeadLevel	mu 22	2727	86.6701586.67015	8.683418.68341

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Part 1

a. Use a

0.010.01

significance level to test the claim that the mean IQ score of people with low blood lead levels is higher than the mean IQ score of people with high blood lead levels.

What are the null and alternative hypotheses? Assume that population 1 consists of subjects with low lead levels and population 2 consists of subjects with high lead levels.

A.

Upper H 0H0:

mu 11less than or equalsmu 22

Upper H 1H1:

mu 11greater than>mu 22

B.

Upper H 0H0:

mu 11equals=mu 22

Upper H 1H1:

mu 11not equalsmu 22

C.

Upper H 0H0:

mu 11not equalsmu 22

Upper H 1H1:

mu 11greater than>mu 22

D.

Upper H 0H0:

mu 11equals=mu 22

Upper H 1H1:

mu 11greater than>mu 22

Part 2

The test statistic is

enter your response here.

(Round to two decimal places as needed.)

Part 3

The P-value is

enter your response here.

(Round to three decimal places as needed.)

Part 4

State the conclusion for the test.

A.

RejectReject

the null hypothesis. There

is notisnot

sufficient evidence to support the claim that subjects with low lead levels have higher IQ scores.

B.

Fail to rejectFailtoreject

the null hypothesis. There

isis

sufficient evidence to support the claim that subjects with low lead levels have higher IQ scores.

C.

RejectReject

the null hypothesis. There

isis

sufficient evidence to support the claim that subjects with low lead levels have higher IQ scores.

D.

Fail to rejectFailtoreject

the null hypothesis. There

is notisnot

sufficient evidence to support the claim that subjects with low lead levels have higher IQ scores.

Part 5

b. Construct a confidence interval appropriate for the hypothesis test in part (a).

enter your response hereless than

(Round to one decimal place as needed.)

Part 6

c. Does exposure to lead appear to have an effect on IQ scores?

No,

Yes,

because the confidence interval contains

only positive values.

zero.

only negative values.