b Provide a 95 confidence interval for the population mean Now we are to find a 95 confidence interval We will use the same formula used when constructing the 90 confidence interval x n The sample mean standard deviation and sample size remain the same Only Za 2 will be different To find the new value of z 2 we must first solve 1 a 0 95 to obtain our value of a Thus a 0 05 giving 2 za 2 Confidence Level 90 95 99 a NR 2 za 2 0 10 0 05 1 645 0 05 0 025 1 960 0 01 0 005 2 576 For a 95 confidence level the necessary value for Za 2 is Use the table below to find the corresponding value for