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Answer:
The 90% confidence interval for population mean is
Step-by-step explanation:
From the question we are told that
The sample mean is
The confidence level is
The sample size is
The standard deviation
Now given that the confidence level is 0.90 the level of significance is mathematically evaluated as
Next we obtain the critical value of from the standardized normal distribution table. The values is
The reason we are obtaining critical values for instead of that of
is because
represents the area under the normal curve where the confidence level 1 -
(90%) did not cover which include both the left and right tail while
is just considering the area of one tail which is what we required calculate the margin of error
Generally the margin of error is mathematically evaluated as
substituting values
The 90% confidence level interval is mathematically represented as
substituting values