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Finding Critical Values In constructing confidence intervals for or 2, Table A-4 can be used to find the critical values L2and R2only for select values of n up to 101, so the number of degrees of freedom is 100 or smaller. For larger numbers of degrees of freedom, we can approximate L2andR2 by using,

2=12z2+2k-12

where k is the number of degrees of freedom and z2is the critical z score described in Section 7-1. Use this approximation to find the critical values L2and R2for Exercise 8 鈥淗eights of Men,鈥 where the sample size is 153 and the confidence level is 99%. How do the results compare to the actual critical values of L2= 110.846 and R2= 200.657?

Short Answer

Expert verified

The calculated values are as follows.

L2=109.980R2=199.655

Both values are quite close to the actual critical values.

Step by step solution

01

Given information

The sample size is 153(n).

The confidence level is 99%.

The actual critical values are L2=110.84andR2=200.657

02

Calculate the critical z-score 

The z-score is obtained from the standard normal table.

The significance level is 0.01, corresponding to a 99% level of confidence.

The critical value is expressed as follows.

PZ>z2=2PZ>z0.012=0.012PZ<z0.005=0.995

By using technology, the critical value is computed as z0.012=2.575829303.

03

Compute the degree of freedom

The degree of freedom is computed as follows.

df=n-1=153-1=152

04

Compute the critical values 

Use the given formula for calculation.

2=12[z2+2k-1]

Substitute the value in the formula as shown below.

L2=12-2.575829303+2152-12=109.9803R2=122.575829303+2152-12=199.6546

Therefore, the values are 109.980 and 199.655, respectively, which are close to the actual critical values L2=110.84and R2=200.657.

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