A group of civil engineering students investigated the 7-day compressive strength of concrete cured using two different chemical additives: Additive Alpha and Additive Beta.
They recorded the compressive strength (in MPa) achieved across five independent batches for each additive. These results are shown in Table 1.
| Batch | Compressive strength for Additive Alpha (MPa) | Compressive strength for Additive Beta (MPa) |
|---|---|---|
| 1 | 42.5 | 36.0 |
| 2 | 43.0 | 36.0 |
| 3 | 42.5 | 36.5 |
| 4 | 18.5 | 36.0 |
| 5 | 43.5 | 35.5 |
| Mean | 38.0 | 36.0 |
| Mode | 42.5 | 36.0 |
| Median | 42.5 | 36.0 |
One of the students made the following statement:
'I think the mean is a more representative measure of the typical compressive strength achieved using Additive Alpha than the median or mode.'
Evaluate the student's statement using the data in Table 1.
The students wanted to know whether there was a significant difference between the 7-day compressive strengths of concrete cured with Additive Alpha and Additive Beta under standard laboratory conditions. They prepared 15 independent batches for each additive and measured their strengths.
Suggest the most appropriate statistical test for the students to use and explain why this test is appropriate.
