20 Basic Statistical Terms

Population?

The entire group you want to study. Example: All students in a university.

Sample?

A smaller group selected from the population to represent it. Example: 100 students from a university.

Variable?

A characteristic or quality that can change. Example: Age, height, or exam scores.

Data?

Information collected about variables. Example: Ages of 100 students.

Mean (Average)?

The sum of all data values divided by the number of values. Example: (10 + 20 + 30) ÷ 3 = 20.

Median?

The middle value when data is arranged in order. Example: For 10, 20, 30, the median is 20.

Mode?

The value that occurs most often in a dataset. Example: In 10, 10, 20, 30, the mode is 10.

Range?

The difference between the highest and lowest values. Example: If values are 10 and 30, the range is 20.

Standard Deviation (SD)?

A measure of how spread out the data is from the mean. Lower SD means data is close to the average.

Variance?

The average of the squared differences from the mean. It’s used to calculate standard deviation.

Probability?

The chance of an event happening. Example: The probability of flipping a coin and getting heads is 50%.

Outlier?

A data point that is far away from others. Example: In 10, 20, 30, 100, the value 100 is an outlier.

Correlation?

A measure of how two variables are related. Positive correlation means they move in the same direction, negative means the opposite.

Regression?

A method to predict one variable based on another. Example: Predicting sales based on advertising spend.

Frequency?

The number of times a value appears in data. Example: If 10 appears 5 times, its frequency is 5.

Probability Distribution?

A chart or formula that shows all possible outcomes and their probabilities. Example: The probability of rolling each side of a die.

Hypothesis?

A statement you test in research. Example: "Studying more hours increases test scores."

P-value?

The probability that your results happened by chance. A smaller p-value means stronger evidence.

Confidence Interval (CI)?

A range that likely contains the true value of a parameter. Example: "The average score is between 50 and 60."

Chi-Square Test?

A statistical test to check if observed results match expected ones. Example: Comparing survey results to predicted responses.