Question

Strength of concrete: The compressive strength in kilopascals, was measured for concrete blocks from five different batches of concrete, both three and six days after pouring. The data are as follows: Batch 2 1372 1313 1 1379 1337 After 6 days After 3 days 3 1365 1352 4 1382 1358 5 1358 1322 Send data to Excel Part: 0/2 Part 1 of 2 (a) Construct a 99.8% confidence interval for the difference between the mean strengths of blocks cured three days and blocks cured six days. Let d represent the strength of blocks cured six days minus the strength of blocks cured three days. Use the TI-84 calculator and round answers to at least one decimal place. A 99.8% confidence interval for the difference between the mean strengths of blocks cured three days and blocks cured six days is <td <0.

Answer 1

The statistical software output for this problem is :

Paired T confidence interval: HD H1 - H2: Mean of the difference between Aftr 6 days and After 3 days 99.8% confidence interval results: Difference Mean Std. Err. DF L. Limit U. Limit Aftr 6 days - After 3 days 34.8 7.8447435 4 -21.471775 91.071775

A 99.8% CI is :

-21.5 $< \mu d <$ 91.1