Cowrie shells have been used as money in many parts of the world, for example, China and Africa. Today, they are used in decorations and jewelry, and cowrie-shell bracelets and necklaces are popular...

Cowrie shells have been used as money in many parts of the world, for example, China and Africa. Today, they are used in decorations and jewelry, and cowrie-shell bracelets and necklaces are popular near seaside resorts. A jeweler recently purchased several hundred cowrie shells to use in making earrings. A random sample of the finished earrings was obtained, and the weight (in grams) of each is given in the table below

a. Find a point estimate for the first quartile and a point estimate for the third quartile.

b. The smallest (in weight) 20% of all cowrie-shell earrings are sold at a discount. Find a point estimate for the 20th percentile of the cowrie-shell earring weight distribution.

A company that manufactures a centrifugal pump for golf ourse sprayers would like to rate the pressure (in psi) developed by this unit. Thirty pumps were randomly selected and tested.

a. Find a point estimate for the minimum pressure developed by this pump.

 b. Find a point estimate for the maximum pressure developed by this pump.

c. Use your answers to parts (a) and (b) to construct an interval estimate for the pressure developed by this pump