Question

Digital Camera Prices The prices (in dollars) for a particular model of digital camera with 6 megapixels and an optical 3X zoom lens are shown below for 9 online retailers. Round sample statistics and final answers to at least one decimal place.

221 180 200 187 265 222 197 195 181

Estimate the true mean price for this particular model with

90% confidence. Assume the variable is normally distributed.

Answer 1

We can find the sample mean and standard deviation of the given data set using excel function =AVERAGE( ) and =STDEV.S() respectively.

We have : = 205.33 , s = 27.0601 , n = 9 and confidence level = 0.90

α = 1- 0.90 = 0.1 and df = n -1 = 8  

Therefore t(0.1,8) = 1.86

Confidence interval :

=

=

=188.6 and 222.1

90% confidence for the true mean price for this particular model is ( 188.6 , 222.1 )