A company that specializes in products for home gardening has developed a new plant food that has been designed to increase the growing height of plants. The new plant food that has been tested on a sample of 12 plants of a type known to have a mean growing height of 18 inches. Results showed a sample mean height of 19.4 inches and a sample standard deviation of 3 inches. Assume that the heights of the plants are normally distributed. Using a .10 level of significance, is there reason to believe that the new plant food increases plant height?
H0: = 18
Ha: > 18
Test statistics
t = - / S / sqrt(n)
= 19.4 - 18 / 3 / sqrt(12)
= 1.62
This is test statistics value.
Critical value at 0.10 level with 11 df = 1.363
Since test statistics value > 1.363, we have sufficient evidence to reject H0.
We conclude at 0.10 level that we have sufficient evidence to support the claim.
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