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Chapter 7: Q4 (page 351)

LeftiesThere have been several studies conducted in an attempt to identify ways in which left-handed people are different from those who are right handed. Assume that you want to estimate the mean IQ of all left-handed adults. How many random left-handed adults must be tested in order to be 99% confident that the mean IQ of the sample group is within four IQ points of the mean IQ of all left-handed adults? Assume that is known to be 15.

Short Answer

Expert verified

The number of left-handed adults that must be tested in order to be 99% confident that the mean IQ of the sample group is within four IQ points of the mean IQ of all left-handed adults is 94.

Step by step solution

01

Given information

The level of confidence is 99%.

The margin of error is E=4.

The population standard deviation is 蟽=15.

02

Compute the sample size

The level of confidence is 99%, which implies that the level of significance is 0.01.

From the Z table, the critical value at 0.01 level of significance is 2.5758.

The number of left-handed adults that must be tested in order to be 99% confidentthat the mean IQ of the sample group is within four IQ points of the mean IQ of all left-handed adults is computed as follows:

n=(z伪2脳蟽)2E2=2.57582脳15242=93.301鈮�94

Therefore, the number ofleft-handed adults that must be tested is 94.

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