Diamond Pricing. In a Singapore edition of Business Times, diamond pricing was explored. The price of a diamond is based on the diamond’s weight, color, and clarity. A simple random sample of 18 one-half-carat diamonds had the following prices, in dollars.

1676 1442 1995 1718 1826 2071 1947 1983 2146 1995 1876 2032 1988 2071 2234 2108 1941 2316

a. Apply the t-interval procedure to these data to find a 90% confidence interval for the mean price of all one-half-carat diamonds.

Interpret your result. (Note: x¯ = $1964.7 and s = $206.5.)

b. Obtain a normal probability plot, a boxplot, a histogram, and a stem-and-leaf diagram of the data.

c. Based on your graphs from part (b), is it reasonable to apply the t-interval procedure as you did in part (a)? Explain your answer.