5.4.2 - Statistical and Practical Significance

Our decision in the Penn State example was to reject the null hypothesis and conclude that the proportion of Penn State students who like the cold was not 0.5. However, our sample proportion of 0.556 wasn't too far off from 0.5. What do you think of our conclusion? Yes, statistically there was a difference at the 5% level of significance, but are we "impressed" with the results? That is, do you think 0.556 is really that much different from 0.5?

Here we distinguish between statistical significance and practical significance. Statistical significance is concerned with whether an observed effect is due to chance and practical significance means that the observed effect is large enough to be useful in the real world.