round to the nearest 4 decimal places

we as an organization took a random sample of 21 students to examine the number of hours per week students surf youtube. The sample means response was 6.85 hours and the sample standard deviation was 1.75 hours. Based on these results, and assuming normality for the population distribution of surfing time in hours, the organization constructed a confidence interval extending from 6.23 to 7.25 hours per week for the population mean. What is the confidence level used for this interval?