Researchers at a weather center in the northeastern United States recorded the number of 90° days each year since records first started in 1875. The numbers form a normal shaped distribution with a mean of µ = 9.6 and a standard deviation of σ = 1.9. To see if the data showed any evidence of global warming, they also computed the mean number of 90° days for the most recent n = 4 years and obtained M = 12.25. Do the data indicate that the past 4 years have had significantly more 90° days than would be expected for a random sample from this population? Use a one-tailed test with α = .05, and use the Distributions tool given below to help. The standard error is , and the sample mean corresponds to z = . (Round your answer to two decimal places.) This is well beyond the critical boundary of . the null hypothesis, and conclude that the past 4 years a representative sample from a population with a mean of µ = 9.6.
Researchers at a weather center in the northeastern United States recorded the number of 90° days each year since records first started in 1875. The numbers form a
The standard error is
, and the sample mean corresponds to z =
. (Round your answer to two decimal places.) This is well beyond the critical boundary of . the null hypothesis, and conclude that the past 4 years a representative sample from a population with a mean of µ = 9.6.
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