Assume that we want to construct a confidence

Auria Diaz

Auria Diaz

Answered question

2022-06-24

Assume that we want to construct a confidence interval. Do one of the​ following, as​ appropriate: (a) find the critical value

tα/2​,

​(b) find the critical value

zα/2​,

or​ (c) state that neither the normal distribution nor the t distribution applies.

Here are summary statistics for randomly selected weights of newborn​ girls:

n=277​,

x=28.5

​hg,

s=6.8

hg. The confidence level is

95​%.

Answer & Explanation

Vasquez

Vasquez

Expert2023-05-22Added 669 answers

To construct a confidence interval for the given scenario, we need to determine whether to use the critical value tα/2 or zα/2 based on the sample size and the information provided.
Given that the sample size is n=277 and the confidence level is 95%, we can use the following guideline:
1. If the sample size is large (typically considered as n>30), we use the critical value zα/2 since the sample size is sufficient for the central limit theorem to apply.
2. If the sample size is small (typically considered as n30) or the population standard deviation is unknown, we use the critical value tα/2 based on the t-distribution.
In this case, the sample size n=277 is relatively large, so we'll use the critical value zα/2.
For a confidence level of 95%, the significance level (α) is calculated as 1confidence level=10.95=0.05. Since the confidence interval is two-tailed, we divide α by 2, giving us α/2=0.05/2=0.025.
To find the critical value zα/2, we refer to the standard normal distribution table or use a statistical calculator. For a significance level of α/2=0.025, the corresponding critical value is approximately z0.0251.96.
Therefore, for the given scenario, we use the critical value zα/2=1.96 to construct the confidence interval.

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