Question

Construct a confidence interval for the following data. Be sure to write your answer as an interval. € x= 33, n = 36, σ = 4, Confidence level = 95%

I know the formula but I always get -1.645 for my z value ( Before dividing by two) How is it supposed to come out to 1.96, what am I doing wrong.

Answer #1

Solution :

Given that,

Point estimate = sample mean =
= 33

Population standard deviation =
= 4

Sample size = n = 36

At 95% confidence level

= 1 - 95%

= 1 - 0.95 =0.05

/2
= 0.025

Z/2
= Z_{0.025 = }1.96

Margin of error = E = Z/2
* (
/n)

= 1.96 * ( 4 / 36
)

= 1.31

At 95% confidence interval estimate of the population mean is,

± E

33 ± 1.31

( 31.69, 34.31)

Looking at my answers, I was am always off buy about range of .1
to .4 from the correct answer that is stated. I am having a really
tough time trying to figure out how to get my number to be exactly
like what is shown as correct so I need a little help with figuring
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