# Question

A company receives lightbulbs from two different suppliers. Define the variables x and y by x = lifetime of a bulb from Supplier 1 y = lifetime of a bulb from Supplier 2 Five hundred bulbs from each supplier are tested, and the lifetime of each bulb (in hours) is recorded. The density histograms in Figure EX7.9 below are constructed from these two sets of observations. Although these histograms are constructed using data from only 500 bulbs, they can be considered approximations to the corresponding population distributions.
a. Which population distribution has the larger mean?
b. Which population distribution has the larger standard deviation?
c. Assuming that the cost of the lightbulbs is the same for both suppliers, which supplier would you recommend? Explain.
d. One of the two distributions pictured has a mean of approximately 1000, and the other has a mean of about 900. What is the approximate mean of the distribution for the variable x (lifetime for a bulb made by Supplier 1)?
e. One of the two distributions pictured has a standard deviation of approximately 100, and the other has a standard deviation of about 175. What is the approximate standard deviation of the distribution for the variable x (lifetime for a bulb made by Supplier 1)?

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