What is Critical Value? Definition, Types, & Calculations

Critical value is crucial in statistical analysis as it helps determine the significance of results and aids in making informed decisions based on data. Accurate calculation and interpretation of critical values are essential for reliable statistical analysis.

What is Critical Value

The idea of critical value is crucial while exploring the world of statistics and is of utmost importance. Making judgments about testing hypotheses, calculating confidence intervals for a population-based sample of data, etc. requires understanding a fundamental statistical concept called the crucial value.

For statistical investigations such as hypothesis testing and other ones, the crucial value acts as a guiding criterion. This increases the dependability of statisticians’ findings by assisting them in drawing appropriate inferences from data.

We shall discuss the definition of critical value in this blog. To further understand its practical ramifications, we will go into more detail about its description, its different kinds, and its computation techniques with the help of some examples.

Critical Value:

In statistical hypothesis testing, the critical value is a threshold or boundary that assists in determining whether or not to reject the hypothesis. The desired significance level (α), which denotes the likelihood of making a Type I mistake (wrongly rejecting a valid null hypothesis), is what determines the critical value.

The boundary at which the null hypothesis is accepted or rejected is defined by the critical values. A critical value is fundamentally the threshold at which a statistical test becomes significant.

The null hypothesis, sometimes abbreviated as H0, states that no discernible difference or effect exists. However, scholars frequently attempt to refute this theory with an alternative that contends a distinction exists.

Types of Critical Value:

F – Critical Value:

In both regression analysis and analysis of variance (ANOVA), the F-critical plays an important role. This sort of critical value determines whether to accept or reject the null hypothesis in a variance-based hypothesis test.

The notation Fα, df1, df2, where α is the level of significance and df1, and df2 are the degrees of freedom for the denominator and nominator respectively. These notations are used to denote in most cases.

T – Critical Value:

In hypothesis testing for small sample sizes where the population standard deviation is unknown, the T-critical value is used. It aids in determining whether there is a notable difference between the sample mean and the population mean.

Z – Critical Value:

When there is a large sample size and the data has a normal distribution, the Z-critical value is used. It frequently applies to means and proportions.

Chi-Square Critical Value:

In tests of independence and goodness-of-fit, the Chi-square critical value is utilized. It evaluates the relationship among categorical variables.

Calculations of Critical Value:

The level of significance (α), degree of freedom, and kind of statistical test being run (conducted) are all variables that affect how a critical value is calculated. As an interpretation, typically normal distribution tables may be used to determine the critical value in a Z-test.

The selected significance level, the test type (one-tailed or two-tailed), and the sample size all have an effect on the critical value. Different critical values can result from adjusting these components.

F – Score Calculation:

The denominator and numerator of the computation both have degrees of freedom. In order to determine the F-critical value for the selected alpha level, researchers employ statistical tables or software.

T – Score Calculation:

The necessary T-critical value is provided by tables or software dependent on the alpha level, much like with the F-critical value. The T-distribution is used to calculate the critical values when working with limited sample sizes or when the population standard deviation is unknown.

This frequently occurs when data does not conform to the expectations of a normal distribution.

Z – Score Calculation:

Z-scores are a common format for writing critical values for a normal distribution. Z-scores help to determine the precise point on this type of distribution curve beyond which the null hypothesis is rejected.

The Z-critical value, in contrast to earlier critical values, directly relates to the selected alpha level. To discover it, researchers utilize software or the common normal distribution table.

Chi-square Score Calculation:

In this case, degrees of freedom are also significant. Researchers use statistical tables or tools to establish the Chi-square critical value.

Example of Critical Value:


Consider a sample of 40 hypertensive individuals who were chosen. Examine the statistical significance of the mean drop in blood pressure following drug use at a 95% confidence level. The population’s standard deviation is unknown, while the sample mean is 9mmHg.


Step 1: Given data

Sample mean (x̄) = 9 mmHg (decreased in blood pressure)

Sample size (n) = 40

Significance level (α) = 0.05 (95% confidence level)

Degrees of freedom (df) = n – 1 = 40 – 1 = 39

Step 2: We will utilize the t-distribution to determine the crucial value because we have a limited sample size and an unknowable population standard deviation.

A t-critical calculator may be used to determine the t-critical value for a two-tailed test with 39 degrees of freedom at a 0.05 significance level. The calculator provides an approximate result of 2.021.

Step 3: T-test formula is:

t = (x̄ – μ) / (s / √n) (μ is the hypothesized population mean)

Assume that the sample standard deviation is 5 and the hypothesized population mean is 0 (no decrease in blood pressure under the null hypothesis).

t = (9 – 0) / (5 / √40) ≈ 11.38

We reject the null hypothesis because the estimated t-test statistic (11.38) is higher than the t-critical value (2.021). This may indicate that the medication’s ability to lower blood pressure is statistically significant.

This example highlights the significance of critical values in various statistical tests, which are crucial for assessing the importance of results and formulating informed hypotheses. For those dealing with t-distribution problems, a t table calculator by MeraCalculator can simplify the process of finding the t critical value.

Wrap Up:

Critical values are crucial to the area of statistics since they help researchers and analysts make judgments based on statistical tests. In order to understand the notion of crucial value, we have covered its definition, kinds, and applications in this article blog. We have also looked at several key computations.

Leave a Comment