Two different groups in a statistics class are conducting a survey to estimate the mean number of units students at their college are enrolled in. the population mean and standard deviation are unknown. the sample from the first group survey has 49 data values. the sample from the second group survey has 81 data values. for each sample, the groups construct a 90% confidence interval to estimate the population mean. which confidence interval will have greater precision (smaller width) for estimating the population mean?