I need help on step 4

e nswer to Find Ex by adding all of the values of the observations together. Then use that number to calculate the sample mean. Recall that n = 9. (Round your answe four decimal places.) 5 - v [1272333 Step 3 Recall that the formula for the sample standard deviation. Sx? - (EI)Z g = n \\ n=1i Recall that Ex = 11,451knd n =9, Find x2 by squaring each observation and then by adding the results together. Then use the sum of the squared observations to calculate the sample standard deviation. (Round your answer to four decimal places.) [ | | | | Y T (Ex) 2 = }LX n \\ n N . W' b 3 '_; 14,577,183| - 1:,:512 \\ s - B0 | 31.0121 [ e | (b) Find a 90% confidence interval for the mean of all tree-ring dates from this archaeological site. To find a confidence interval for the mean of all tree-ring dates from this archaeological site, you will need a point estimate for u, and you will either need to know the population standard deviation or estimate it in order to calculate the margin of error. In the previous step you calculated the sample mean, x = 1,272.3333, Use this as your point estimate for u. You also calculated the sample st s = 31,0121 andard deviation, To compute a confidence interval for u, you will need a critical value from Student's distribution with n 1 degrees of freedom representing the t-critical value such that an area equal to under the t curve falls between This number, t_, is the number f( and t_. Find the critical value for a confidence level of 90% We found earlier that n = 9, thus the degrees of freedom are n l= Find t., the t-critical value to.90 =