To celebrate their fi rst anniversary, Randy Nelson decided to buy a pair of diamond earrings for his wife Debbie. He was shown nine pairs with marquise gems weighing approximately 2 carats per pair. Because of differences in the colors and qualities of the stones, the prices varied from set to set. The average price was $2,990, and the sample standard deviation was $370. He also looked at six pairs with pear-shaped stones of the same 2-carat approximate weight. These earrings had an average price of $3,065, and the standard deviation was $805. On the basis of this evidence, can Randy conclude (at a signifi cance level of 0.05) that pearshaped diamonds cost more, on average, than marquise diamonds?
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