Answer: Option 'a' is correct.
Step-by-step explanation:
To construct a confidence interval, we have four steps to do:
1) Recognise the sample statistic by calculating the sample mean and sample variance.
2) Recognise the confidence level i.e. 90%, 95% etc.
3) Calculate the margin of error :
As we know that Margin of error = Critical value × Standard deviation
Now, critical value in case of t - test,
4) find the confidence interval which is given below:
Confidence interval = Margin of error + Sample statistics
So, Option 'a' is correct.
