Problem 7E

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 presented in the following table.

Can you conclude that the mean strength after six days is greater than the mean strength after three days?

Key Vocab Tips Chapter 15: Frequencies and Distributions Distribution of Large data: frequency the value occurs - Helps to better understand frequency in large data set - Estimates distribution shape or population from sample distribution shape Frequency Table Normal Distribution - Large sample from the population should be normally distributed - Bell Shaped Curve: Gaussian curves > Gauss created complicated stats Skewed Distribution - Negative: easy test; values cluster at top *ceiling effect* - Positive: Hard test; values cluster at bottom *floor effect* - Kurtosis: shape of curve How to remember positive and negative skewed dis