ESS210B
Prof. Jin-Yi Yu
An Example – cont.
qIn an experiment, forty measurements of air temperature were made. The mean and standard deviation of the sample are:
q                              x = 18.41°C    and   s = 0.6283°C.
q
qQuestion 2:
q     How many measurements would be required to reduce the 95% confidence interval for the population mean to (x-0.1)°C to (x+0.1)°C?
q
qAnswer:
q      We want to have Z95% * s / (N)0.5 = 0.1 °C
q      We already know Z95% = 1.96 and s = 0.6283°C
q      è N = (1.96´0.6283/0.1)2 = 152
q