Define statistical significance.

Define statistical significance.

• A. A result unlikely to occur by random chance alone, according to a pre-determined alpha level (often 0.05).
• B. A measure of practical importance.
• C. A sample size calculation.
• D. The frequency of data collection.

Answer: (A)

Statistical significance tells us whether a result is unlikely to occur by random chance under the null hypothesis, using a pre-set threshold for randomness (an alpha level, commonly 0.05). When the observed effect is so unlikely under the null that the p-value falls below that threshold, we say the result is statistically significant, meaning it’s not easily explained by random variation alone. This concept hinges on comparing the data to what would be expected if there were no real effect, not on how large or important the effect is in the real world. It also isn’t about planning how many samples to collect or how often data are gathered, and it doesn’t automatically imply practical importance or real-world impact.

Statistical significance tells us whether a result is unlikely to occur by random chance under the null hypothesis, using a pre-set threshold for randomness (an alpha level, commonly 0.05). When the observed effect is so unlikely under the null that the p-value falls below that threshold, we say the result is statistically significant, meaning it’s not easily explained by random variation alone. This concept hinges on comparing the data to what would be expected if there were no real effect, not on how large or important the effect is in the real world. It also isn’t about planning how many samples to collect or how often data are gathered, and it doesn’t automatically imply practical importance or real-world impact.