probability questions plz help!! An engineer wishes to estimate the mean setting time of a new cement mix used in highway spot repairs. From a record of setting times for 10 spot repairs he obtain x = 25; 25; 24; 23; 25; 26; 23; 24; 22; 23 minutes, respectively. (a) Find the mean and standard deviation of the setting time. (b) Find a 95% confidence interval for the mean setting time if the standard deviation is known to be ¾ = 1:5 min: Assume a normal distribution (c) Find a 95% confidence interval for for the mean setting time if the standard deviation is unknown.