Descriptive statistics review in Data Analysis Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the mean in descriptive statistics?

The mean is the average value of a dataset. You add all numbers together and divide by how many numbers there are.

beginner

What does the median represent in a dataset?

The median is the middle value when the data is sorted from smallest to largest. It splits the data into two equal halves.

intermediate

Explain the difference between variance and standard deviation.

Variance measures how spread out the data is by averaging the squared differences from the mean. Standard deviation is the square root of variance and shows spread in the original units.

intermediate

What is the purpose of the interquartile range (IQR)?

IQR measures the middle 50% spread of the data. It is the difference between the 75th percentile (Q3) and the 25th percentile (Q1). It helps identify outliers.

intermediate

How does skewness describe a dataset?

Skewness shows if the data leans more to one side. Positive skew means a longer tail on the right, negative skew means a longer tail on the left.

Which measure of central tendency is least affected by extreme values?

A Mean

B Median

C Mode

D Range

The median is the middle value and is not affected by very high or low values, unlike the mean.

What does a high standard deviation indicate about a dataset?

A Data points are spread out from the mean

B Data points are close to the mean

C Data has no variation

D Data is skewed

A high standard deviation means data points are more spread out from the average.

The interquartile range (IQR) is calculated as:

A Q1 - Q3

B Mean - Median

C Q3 - Q1

D Max - Min

IQR is the difference between the 75th percentile (Q3) and the 25th percentile (Q1).

If a dataset has a skewness close to zero, it means:

A Data is perfectly symmetrical

B Data is heavily skewed right

C Data is heavily skewed left

D Data has many outliers

Skewness near zero means the data distribution is roughly symmetrical.

Which descriptive statistic tells you the most frequent value in a dataset?

A Mean

B Median

C Variance

D Mode

Mode is the value that appears most often in the data.

Describe the main measures of central tendency and when to use each.

Think about average, middle value, and most common value.

Explain how spread or variability in data is measured and why it matters.

Consider how data points differ from the average.