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Snowcat [4.5K]
2 years ago
6

A 99% confidence interval (in inches) for the mean height of a population is 65.7 < μ < 67.3. This result is based on a sa

mple of size 144.
Construct the 95% confidence interval. (Hint: you will first need to find the sample mean and sample standard deviation).
Mathematics
1 answer:
Wittaler [7]2 years ago
3 0

Answer:

66.5 -1.976* 0.3065= 65.89

66.5 +1.976* 0.3065= 67.11

And the 95% confidence interval would be givne by (65.89; 67.11)

Step-by-step explanation:

For this case we have a 99% confidence interval for the true mean hegiht givne by:

65.7 \leq \mu \leq 67.3

And we can begin finding the mean with this formula:

\bar X= \frac{65.7 +67.3}{2}= 66.5

Now we can estimate the margin of error:

ME = \frac{67.3-65.7}{2}= 0.8

The sample size for this case is n = 144 then the degrees of freedom are given by:

df = n-1= 144-1=143

And then we can find a critical value for a 99% of confidence and 143 degrees of freedom using a significance level of 0.01 and we got:

t_{\alpha/2}= 2.61

Then the standard error is given by:

SE = \frac{ME}{t_{\alpha/2}}= \frac{0.8}{2.61}= 0.3065

Now we can find the other critical value for 95% of confidence and we got:

t_{\alpha/2}= 1.976

And the new confidence interval would be given by:

66.5 -1.976* 0.3065= 65.89

66.5 +1.976* 0.3065= 67.11

And the 95% confidence interval would be givne by (65.89; 67.11)

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