Question

0ft	10ft	30ft	40ft
0.045	0.045	0.044	0.098
0.043	0.031	0.044	0.074
0.04	0.043	0.048	0.154

The dataset contains measurements of iron levels at several depths in a bay. Develop your hypotheses and at .05 significance level conduct the appropriate statistical test to determine if iron levels are different at different depths. If they are, at .05 significance level, conduct follow up tests to determine which groups are different from each other. Build the ANOVA table. Select all the groups that are significantly different from each other:

Select all the groups that are significantly different from each other:

Select one or more:

a. 0 ft and 10 ft

b. 0 ft and 30 ft

c. 0 ft and 40 ft

d. 10 ft and 30 ft

e. 10 ft and 40 ft

f. 30 ft and 40 ft

Answer 1

To test whether means of all groups are same or not, we need to use Oneway ANOVA.

Using Minitab software, (Stat -> ANOVA -> One way),we get the following output :

Since the value of the test statistic = 7.51 and P-value = 0.01 < 0.05, so at 5% level of significance, we reject the null hypothesis and we can conclude that mean of all 4 groups are significantly different.

So, we need to use pairwise comparison tests to check which means are significantly different.

Since only p-value for 40ft - 10ft = 0.016 < 0.05, so we reject H₀ at 0.05 level of significance and we can conclude that means of groups 10ft and 40ft are significantly different.

ans-> e) 10 ft and 40 ft