You work for a company that produces electronics with integrated circuits.  One of your products is called a "shift register."  This product is designed to automatically shut down if its operating temperature exceeds 175 degrees Celsius.  The manufacturing process has been designed to have a standard deviation of $\displaystyle \sigma={0.4}$ degrees Celsius.  You test a random sample 19 shift registers, and you record the following shut-down temperatures. Construct a 98% confidence interval for the overall mean shutdown-temperature.

174.76	175.81	174.57	174.94	175.14	174.79	175.19
175.11	175.16	175.15	174.99	174.92	174.51	174.43
175.08	174.8	175.34	175.26	174.19

(Checksum: 3324.14)

 

a) Find the critical value and $\displaystyle \sigma_{\overline{{{x}}}}$ .

Critical Value:     $\displaystyle \sigma_{\overline{{{x}}}}$ :

b)  Find the confidence interval:  (,)