T-Score vs. Z-Score: A Complete Analysis

Home » T-Score vs. Z-Score: A Complete Analysis

If you are new to statistics, you may not be familiar with various crucial statistical terms like The T-Score and the Z-score. They are indispensable for hypothesis testing. T-Score examines the standard deviation from the T distribution. In contrast, Z-score determines the standard deviation of a data point from the mean of a distribution. If you are intrigued to learn more about the dissimilarities of the T-Score vs. Z-Score, read this blog. Here we have performed a comparative study of the two widely used data comparison and assessment techniques.

A Comparative Study of T-Score Vs. Z-Score

T-Score vs. Z-Score

Here is a comparison between the T-score and the Z-score.

T-score vs. Z-score: Concept

The concept of the T-score is quite different from that of the Z-score. Here is the difference between the two:

  • What is a T-score?

A T-score is the distance between a data point and the mean in a t-distribution. It is measured with the help of standard deviations. You may also call the T-score a statistical technique for examining probability. The t-distribution is a typical distribution formed in the shape of a bell. It is maximum in the center and minimum at both ends and tails. The area below symbolizes the probability of observations. Therefore, most data points have a higher chance to be close to the middle of the graph. In contrast, fewer points have the highest probability to be on the highest or lowest sections. They are characterized by the smaller area in the direction of the tails of the graph.

The t-score is a test that statisticians use for understanding how data match up to to the expected results. They create results similar to the Z-score in the case of data sets that have 30 or more observations. However, the t-score offers more precise results with smaller data sample sizes.

v  What is a Z-Score?

A Z-score is a statistical calculation that showcases a value’s connection to the mean of a group of values. The Z-score is calculated in terms of standard deviations from the mean. If a Z-score is 0, it specifies that the data point’s score is the same as the mean score. A Z-score of 1.0 signifies a value that is one standard deviation from the mean. A Z-score may be positive or negative. Here, a positive value refers to the score which is above the mean and a negative score represents it is below the mean.

T-score vs. Z-score: Formula

The formula you use to find the values of the T-score is not the same as the one you use to get the values of the Z-score. The difference between their formulas is mentioned below:

  • Formula to measure a T-score

Here is the rule for calculating a t-score for a one-sample test:

t = (x̄ − μ0) / s x √ n


  • x̄ = sample mean
  • μ0 = population mean
  • s = sample standard deviation
  • n = sample size


  • Formula to calculate a Z-Score

The statistical formula for a value’s z-score is measured using the following formula:

z = ( x – μ ) / σ


  • z = Z-score
  • x = the value being evaluated
  • μ = the mean
  • σ = the standard deviation

Also read: Best Statistics Project Ideas to Get Started

T-score vs. Z-score: Steps to find out the Values

Here is the difference in the steps that you must take to find out the values of the T-score and Z-score.

  • Steps To Find The T-Score Balance

Stick to these steps to find the value of the T-score balance:

  1. Find information about the sample

To start, identify the sample size of the data set and then measure the sample mean and sample standard deviation. The sample size refers to the number of data points. The mean, or average, of a data set refers to the sum of each data point separated by the sample size. You may measure the standard deviation manually with the formula or with a calculator.

Example: A biology investigator gathers data about the local skink population and would like to measure how the local skink length contrasts with the species’ average. So far, she has observed four skinks: Two that are 12 cm long, one that is 13 cm, and one that is 14 cm. From this information, she estimates the following values about her data:

  • Sample size = n = 4
  • Sample mean = x̄ = 12.75
  • Sample standard deviation = s = 0.9574
  1. Determine the mean of the population

In a one-sample test, you can compare a set of data to a known or theorized population means. To discover this population mean, you can take a look at the arrangement of the question, or consider the situation where you implement the t-score. The populations mean refers to the figure that you work on to establish or disprove with your calculations: an average test score, height, or length of time.

Example: The skink researcher finds in a peer-reviewed paper that other researchers have calculated the average length for this species of skink to be 12 cm, so that’s the population mean, or μ0, for her calculation.

  1. Enter information into the formula

When you have collected all the data you require, implement the numbers into the t-score formula for a one-sample test. As one of the aspects is the square root of n when your data set only has one observation, you can employ a simplified version of the formula:

t = (x-μ0) / s

Example: The skink researcher enters her numbers into the t-score formula for a one-sample test:

t = (x̄ − μ0) / s x √ n = (12.75 − 12) / 0.9574 x √ 4

t = 0.75 / 0.9574 x √ 4

t = 0.7834 x 2

t = 1.567

  1. Consult a t-score chart

Open the T-score chart at the back of your math textbook and find the value that correspond your evaluated T-Score to get the precise T-score values. To construe these charts, you may require learning several additional terms:

  • Degrees of freedom: It indicates the sample size minus one
  • Confidence interval: The percentage probability that you may from your data
  • Alpha level: 1 − the confidence interval, sometimes employed as substituting labeling in place of a confidence interval
  • How to Calculate Z-Score?

You can calculate the Z-score manually and through spreadsheets.

  • Manually

To find the balance of the Z-score manually, you must first determine the mean and standard deviation of your data. Once you have these data, you can measure your z-score. Assume, you have the following variables:

  • x = 57
  • μ = 52
  • σ = 4

Now use the variables in the formula.

  • z = ( 57 – 52 ) / 4
  • z = 1.25

So, the Z-score you get is 1.25.

  • Spreadsheets

To find out the z-score using a spreadsheet, you must input your values and find out the average for the range and the standard deviation using the following formulas:



You will find that the following quantity has a mean of 12.17 and a standard deviation of 6.4.

1 Factor (x) Mean (μ) St. Dev. (σ)
2 3 12.17 6.4
3 13 12.17 6.4
4 8 12.17 6.4
5 21 12.17 6.4
6 17 12.17 6.4
7 11 12.17 6.4

Using the z-score formula, you can determine the z-score of each factor. Use the subsequent formula in D2, then D3, and so on:

Cell D2 = ( A2 – B2 ) / C2

Cell D3 = ( A3 – B3 ) / C3

1 Factor (x) Mean (μ) St. Dev. (σ) Z-Score
2 3 12.17 6.4 -1.43
3 13 12.17 6.4 0.13
4 8 12.17 6.4 -0.65
5 21 12.17 6.4 1.38
6 17 12.17 6.4 0.75
7 11 12.17 6.4 -0.18

Read more: Top Uses of Statistics in Everyday Life

T-Score vs. Z-score: Uses

Following are the differences between the T-score and the Z-score based on their uses.

  • Applications of T-Score

A T Score is applied in the following situations:

  1. Hypothesis Testing: In hypothetical testing, a T-score helps in determining the significance of the observed differences between sample means.
  2. Comparing Group Means: The T scores helps to compare the average of two or more groups. It offers information on the importance of the observed differences between groups.
  3. Confidence Intervals: The T scores play a fundamental role in calculating confidence intervals for a range of conceivable values of the population mean.
  • Uses of Z-Score

A Z-score is used in the following cases:

  1. Standardization: Translating observations or data points into the Z scores helps to compare and assess values quite easily.
  2. Probability and Percentile Calculation: The Z scores help to assess the possibility of the occurrence of an event based on its position compared with the mean in a normal distribution.
  3. Quality Control: The Z scores are used in quality control processes. It helps to examine the inconsistency and adherence to standards in manufacturing or production.

A T-Score vs. a Z-score: Use Cases and Examples

Consider the following use cases and examples to get a better understanding of the practical uses of the T-scores and the Z-scores

  • Use Cases of T Score

Following are the real-life examples of the uses of T-score:

  1. Medical Research: In a clinical trial to evaluate the efficacy of two drugs, researchers may employ T scores to examine and establish if there is a pertinent difference in the treatment outcomes between the two groups.
  2. Educational Testing: When teachers assess the performance of students, a T score helps in comparing individual scores to the average scores in the class. This, in turn, helps to examine the efficiency of an educational intervention.
  3. Market Research: Researchers can use the T-scores to analyze survey data. It helps to determine the statistical significance of the difference in the preferences or opinions of diverse demographic groups.
  • Z Score Use Cases:

Here are the practical uses cases of a Z-Score:

  1. Finance and Investment: The Z scores help to assess the performance of investments by equating the returns of a particular asset to the overall market performance.
  2. Quality Control in Manufacturing: Z-score can help you recognize defects or deviations in manufacturing processes by examining data related to product specifications. It guarantees that products stand up to the required quality standards.
  3. Anomaly Detection: In anomaly detection algorithms, a Z-score is often used to recognize data points that deviate considerably from the expected patterns or behaviors.

Also read: Learn How To Solve Statistics Problems Easily

T-Score vs. Z-score: Standardization of Data

Here is the difference between the T-score and the Z-score on the grounds of data arrangement.

  • T-score: You can obtain the T-score balances by standardizing sample data.
  • Z-score: To get the Z-score values, population data is standardized.

T-Score vs. Z-score: Size of Data

T-Score and Z-score are used for different sizes of data. The following are the differences:

  • T-score: The T-score is used to measure the following sizes of data:
    • sample data is unknown
    • size of sample data is less than 30
  • Z-Score: The Z score is also used to compute 2 sizes of data:
  • Population is known
  • The size of the population is above 30

T-Score vs. Z-score: Value of Mean

Here is the difference in the value of the mean in the T-score and Z-score:

  • T-Score: In this case, the value of the mean is always 50.
  • Z-Score: Here, the value of the mean is always zero.

T-Score vs. Z-score: Range of values

Following are the differences in the range of values of T-score and Z-score:

  • T-Score: The value of T-Score ranges between 20 and 80.
  • Z-Score: Z-Score’s values range between -3 and 3.

T-Score vs. Z-score: Value of Standard Deviation

The dissimilarity in the values of Standard Deviation between T-Score and Z-Score is as follows:

  • T-Score: The standard deviation of a T-Score is always 10.
  • Z-Score: Its standard deviation is always 1

T-Score vs. Z-score: Popularity

T-Scores and Z-Scores are not equally popular. Here is the distinction in their popularity:

  • Z-Score: A Z-Score only supports large data. Therefore, it is less preferable.
  • T-Score: A T-Score covers a wide range of data. Therefore, it is preferable to the Z-score.

T-Score vs. Z-score: Nature of derived results

The results derived from the T-Score and the Z-Score are quite contrasting. The difference is mentioned below.

  • T-Score: Derived results of the T-Score are always positive.
  • Z-Score: Derived results of the Z-score can be positive or negative.

 T-Score vs. Z-score: Distribution

The distinction between T-Score and Z-Score based on distribution is as follows:

  • T-Score: A T-Score is a constituent of T-Distribution.
  • Z-Score: It is a component of Z-Distribution.

Also read: Types of Charts in Statistics

Tabular Representation of the Differences between T-Score vs. Z-Score

Basis of Comparison T-Score Z-Score


A T-score is the space between a data point and the mean in a t-distribution. Standard deviation is used to measure the data. Z-score showcases the relation of a value to that of the mean of a group of values.
Formula to get the values Here is the formula for calculating a t-score for a one-sample test:

t = (x̄ − μ0) / s x √ n


x̄ = sample mean

μ0 = population mean

s = sample standard deviation

n = sample size


The statistical formula to get a  z-score value is:

z = ( x – μ ) / σ


  • z = Z-score
  • x = the value being evaluated
  • μ = the mean
  • σ = the standard deviation


Steps To Find Out the Values Stick to the following steps to find the values of the T-Score:

·         Gather information regarding the sample

·         Ascertain the mean of the population

·         Place information into the formula

·         Check with a t-score chart



To find the values of Z-Score assume that you have the mentioned variables:

  • x = 57
  • μ = 52
  • σ = 4

Use these variables in the formula:

  • z = ( 57 – 52 ) / 4
  • z = 1.25

Thus, The value of Z-Score is 1.25.

Uses T Score is applied in the following situations:

·         Hypothesis Testing:

·         Comparing Group Means

·         Confidence Intervals:

Z-score is used in the following cases:

  • Standardization
  • Probability and Percentile Calculation.
  • Quality Control


Real-life applications The use cases of the T-score are as follows:

  • Medical Research
  • Educational Testing
  • Market Research
Z-Scores are used in practical life in the following areas:

  • Finance and Investment
  • Quality Control in Manufacturing
  • Anomaly Detection
Standardization of Data T-score balances can be obtained by standardizing sample data. Z-score values can be gained when the population data is standardized.
Size of Data A T-score is used to calculate when the sample data is unknown and the sample data’s size is less than 30


A Z score is also used to compute an unknown population or when the population’s size is above 30


Value of Mean T-Score’s value of the mean is always 50. Z-score’s value of the mean is always zero.
Range of values T-Score’s values range between 20 and 80. Z-Score’s value is always between the range -3 and 3.
Value of Standard Deviation T-Score’s standard deviation is always 10. Z-Score’s standard deviation is always 1
Popularity A T-Score is more popular. A Z-Score is less preferable compared to T-Score.
Nature of derived results T-Score always give positive derived results. Z-score’s derived results can be positive or negative.
Distribution A T-Score is a component of the T-Distribution. It is a part of Z-Distribution.



The T-scores and the Z-scores are dominant statistical tools that help in data investigation, hypothesis testing, and illustration of meaningful conclusions. The discussion above highlights the prominent differences between the T-Score vs. the Z-score. Understanding the dissimilarity, computation, and uses of T scores and Z scores helps researchers, statisticians, and data analysts to formulate informed decisions and deduct accurate conclusions from their data. T scores are best suited for small sample sizes and unidentified population standard deviations. In contrast, the Z-scores are suitable for large sample sizes with identified or predictable population standard deviations. Take advantage of these scores for statistical analysis and take evidence-based decisions.

Jacob Smith Education Reading Time: 13 minutes

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