In: Statistics and Probability
Parents of potential WKU students often express an interest in making sure their child can graduate in 4 years. To do so, students must complete an average of 15 credit hours per semester. A random sample of 250 students at WKU finds that these students take a mean of 14.7 credit hours per semester with a standard deviation of 1.9 credit hours. Assume the sample standard deviation is equal to the population standard deviation. Estimate the mean credit hours taken by a student each semester using a 95% confidence interval. Round to the nearest thousandth. (Note that the options give the answer in the format of sample mean +/- the margin of error).
| 
 14.7 ± .171  | 
||
| 
 14.7 ± .236  | 
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| 
 14.7 ± .015  | 
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| 
 14.7 ± .011  | 
Parents of potential WKU students often express an interest in making sure their child can graduate in 4 years. To do so, students must complete an average of 15 credit hours per semester. A random sample of 250 students at WKU finds that these students take a mean of 14.7 credit hours per semester with a standard deviation of 1.9 credit hours. Assume the sample standard deviation is equal to the population standard deviation.
Now, we estimate the mean credit hours taken by a student each semester using a 95% confidence interval.
Since we assume that sample standard deviation as population standard deviation so we use Z-critical value to estimate the 95% CI.
Given that,
Sample Mean = 14.7 and  
Population Standard Deviation = 1.9 and  
Sample Size = 250
Level of significance:-



Critical Value:-

[ Value are getting from Z-table ]
Margin of Error:-

Now we put the value of 
, 
, 
 and we get,


[ Round to the nearest thousandth ]
95% Confidence Interval For Population Mean:-

Now we put the value of MOE and 
 and we get,

i.e. 95% confidence interval for population mean is
given by,  
Answer:- Correct answer is " 2nd Option "