A bulb manufacturer claims that their bulbs last for 300 days. A researcher randomly selects 15 bulbs for testing. The sampled bulbs last an average of 290 days, with a standard deviation of 50 days. If the company's claim were true, what is the probability that 15 randomly selected bulbs would have an average life of no more than 290 days?

0.22

Step-by-step explanation:

according to company's claim The mean is 300

So you can use the formula (x - mu) / (sigma/sqrt (n))

where x = the value received from the samples bulbs 290

mu = mean 300

sigma = Standard deviation 50

n = bulbs for testing 15

Which will give thi (-0.7746)

which is equal to 1 - thi (0.7746)

using the normal table you can find that thi (0.7746) is 0.78 approximately

1-0.78 = 0.22