Susan is interested in determining whether sunflower seedlings treated with compound A resulted in a lower average height of sunflower seedlings than the standard height of 15.7 cm. She treated a random sample of 10 seedlings with compound A and then recorded their heights: 11.5, 15.2, 16.5, 15.1, 12.9, 9.3, 11.8, 15, 8.5 and 9.5. Assuming sunflower seedlings are normally distributed and that Susan must estimate the standard deviation of this distribution, which of the following statements properly analyzes Susan’s hypothesis? a. She needs to conduct a two-tailed t-test; although the average of the sample is below 15.7 she cannot reject the null hypothesis at the 5% level.
b. She needs to conduct a one-sided t-test; the average of the sample is below 15.7 and statistically significant at the 5% level.
c. She needs to conduct a two-tailed z-test; although the average of the sample is below 15.7 she cannot reject the null hypothesis at the 5% level.
d. She needs to conduct a one-sided z-test; the average of the sample is below 15.7 and statistically significant at the 5% level.
e. She needs to conduct a two-tailed t-test; the average of the sample is below 15.7 and statistically significant at the 5% level.