Descriptive Statistics

Question 1

What is central tendency?

Answer 1

Central tendency describes the typical value in a sample, such as the mean or median.
- Example: The average weight of 50 people.

Question 2

What is dispersion in descriptive statistics?

Answer 2

Dispersion describes how spread out the data are, using measures like variance, standard deviation, and interquartile range (IQR).
- Example: Variance in the heights of students in a classroom.

Question 3

How is the mean calculated?

Answer 3

The mean is calculated by summing all values and dividing by the number of observations.
- For values 3, 4, 5, the mean is (3+4+5)/3 = 4.

Question 4

How is variance calculated?

Answer 4

Variance is the average of the squared differences from the mean.
- If the values are 3, 4, 5 and the mean is 4, variance is ((3-4)² + (4-4)² + (5-4)²)/3 = 0.67.

Question 5

What are quartiles and the interquartile range (IQR)?

Answer 5

Quartiles divide data into four equal parts. The IQR is the range between the 1st and 3rd quartiles, showing the spread of the middle 50% of data.
- Example: For a dataset split into quartiles, the IQR might be between the 25th and 75th percentiles.

Question 6

What is effect size?

Answer 6

Effect size measures the magnitude of the difference between groups. It shows whether a change in the response variable is meaningful.
- A 20% increase in cancer risk from consuming processed meat.

Question 7

How is effect size calculated using differences?

Answer 7

Effect size as a difference is the absolute difference in mean values between groups.
- If Starbucks coffee costs $2.10 and Tim Hortons coffee costs $1.79, the effect size is $2.10 - $1.79 = $0.31.

Question 8

How is effect size calculated using ratios?

Answer 8

Effect size as a ratio compares the relative change in mean values between groups.
- The ratio for Starbucks vs. Tim Hortons coffee prices is $2.10 / $1.79 = 1.17, meaning Starbucks coffee is 17% more expensive.