Stats in Psych Review

Which measure of central tendency is most influenced by outliers?

• mean

• median

• mode

• standard deviation

• histogram

Answer explanation

The mean is most influenced by outliers because it takes into account all values in a dataset. A single extreme value can significantly alter the mean, while the median and mode remain unaffected by such outliers.

What is the range of the following numbers?: 12, 25, 33, 40, 80?

• 68

• 98

• 33

• 38

• 190

Answer explanation

The range is calculated by subtracting the smallest number from the largest. Here, 80 (largest) - 12 (smallest) = 68. Therefore, the correct answer is 68.

In a normal distribution, what percentage of the scores in the distribution falls within one SD of the mean?

• 34%

• 40%

• 50%

• 68%

• 95%

Answer explanation

In a normal distribution, approximately 68% of the scores fall within one standard deviation (SD) of the mean. This is a key property of the normal distribution, making 68% the correct answer.

What does this curve represent?

• A positive skew: there are more high than low scores

• A positive skew: there are more low than high scores

• A negative skew: there are more high than low scores

• A negative skew: there are more low than high scores

Answer explanation

The correct choice is 'A positive skew: there are more low than high scores.' In a positively skewed distribution, the tail on the right side is longer, indicating that there are more low scores and fewer high scores.

Descriptive statistics _________________, while inferential statistics __________________

• indicate the significance of the data; summarize the data

• describe data from experiments; describe data from surveys and case studies.

• are measures of central tendency; are measures of variance.

• determine if data can be generalized to other populations; summarize data

• summarize data; assess if data can be generalized.

Answer explanation

Descriptive statistics summarize data by providing simple summaries about the sample and measures of central tendency. Inferential statistics assess if findings can be generalized to a larger population.

Which of the following statements accurately describes the results of a study that are considered to be statistically significant?

• Observed gender differences in aggression are most likely due to a fluke/chance.

• Observed gender differences in aggression are very important and should be investigated further.

• Observed gender differences in aggression are most likely not due to a fluke/chance, but rather some real effect

• Observed gender differences have much practical significance.

Answer explanation

The correct choice indicates that observed gender differences in aggression are statistically significant, meaning they are unlikely to be due to chance. This suggests a real effect worth further investigation.

A study comparing two diet programs finds that Program A participants lost an average of 8 pounds while Program B participants lost an average of 6 pounds. However, the statistical test shows p = 0.12, indicating the difference is NOT statistically significant. What is the most appropriate conclusion?

• The 2-pound difference proves that Program A is better than Program B, regardless of the p-value.

• The lack of statistical significance means the researchers made an error in their calculations since there is clearly a 2-pound difference.

• The programs are equal in effectiveness.

• We cannot conclude that Program A is more effective than Program B based on this study; the observed difference could reasonably be due to chance.

Answer explanation

Lack of statistical significance means we cannot rule out chance as an explanation for the observed difference. Not finding statistical significance doesn't prove the programs are equal

• It just means we don't have enough evidence to conclude they're different.

True or False?

The results of a study can be statistically significant, yet have small effect size.

• TRUE

• FALSE

Answer explanation

TRUE. A study can show statistically significant results due to a large sample size, but the actual effect size may be small, indicating that while the result is reliable, its practical importance may be limited.