In: Statistics and Probability
Suppose we are interested in the mean scores on an exam. A random sample of 36 scores is taken and gives a sample mean (sample mean score) of 68 (x̄ = 68). In this example, we have the unusual knowledge that the population standard deviation is 3 points. Do not count on knowing the population parameters outside of textbook examples.
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Solution :
Given that,
Z/2
= 1.645
Margin of error = E = Z/2*
(
/
n)
= 1.645 * (3 /
36)
= 0.82
At 90% confidence interval estimate of the population mean is,
- E <
<
+ E
68 - 0.82 <
< 68 + 0.82
67.18 <
< 68.82
(67.18 , 68.82)