What is Null Hypothesis?
The null-hypothesis is considered an accepted truth. It assumes that the research is false, that the observations are caused by random factors. Researchers must prove the null-hypothesis wrong to prove their alternate hypothesis.
The null-hypothesis presumes that the sampled data and the population data have no difference. It is the opposite of the alternate hypothesis, which says that the sample or claimed data differs from the actual population. The null-hypothesis is denoted by H0 (pronounced as ‘H naught’).
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- During, Null Hypothesis Significance Testing (NHST), if the level of significance is within the acceptable limit or confidence interval, H0 is accepted; otherwise, it is rejected.
- Hypothesis testing is a form of a mathematical model that is used to accept or reject a hypothesis within a range of confidence levels.
- Null hypothesis is an assumption that is accepted valid unless proven otherwise. It is used for prove or dissprove research statements along with statistical data.
Null Hypothesis Explained
A null-hypothesis can be defined as an accepted fact that may or may not be true. In the initial claim of the null-hypothesis, it is believed that the assumption is valid. The null hypothesis is mainly used for verifying the relevance of Statistical data taken as a sample. This sample is then compared to the characteristics of the whole population from which the sample was taken. Researchers can prove or disprove a statement or assumption by conducting Hypothesis TestingHypothesis TestingHypothesis Testing is the statistical tool that helps measure the probability of the correctness of the hypothesis result derived after performing the hypothesis on the sample data. It confirms whether the primary hypothesis results derived were correct. (NHST).
For example, assume that a claim states it takes 30 days to form a habit. Therefore, it will be considered that it is valid until there is some statistical significanceStatistical SignificanceStatistical significance is the probability of an observation not being caused by a sampling error. to prove that our assumption is wrong, and it does not take 30 days to form a habit. Hypothesis testing is a mathematical model used to accept or reject the hypothesis within the prescribed range of confidence level. It is also used for verifying the difference between alternative procedures.
The null hypothesis serves as a base for prominent scientific research. For example, scientists believe that “there is life on Mars,” The statement could be accepted or rejected based on statistical analysis.
Null Hypothesis Formula
Based on the null hypothesis, we need to prove that:
A hypothesis is tested for significance levels level in the observed data. This is done for summarizing theoretical data.
For calculation of deviation from the claimed data, we can use the formula:
How to find the null-hypothesis?
Some of the basic steps to determine H0 are as follows:
- The first step is to assume that the given statement is true.
- Next, find the level of significance or the deviation rate. For this first find the difference between claimed data and the actual data and then divide it by claimed data. The result is multiplied by 100.
- If the result falls within the confidence interval, then the null hypothesis is accepted; however, the hypothesis is rejected if it is outside the confidence intervalConfidence IntervalConfidence Interval refers to the degree of uncertainty associated with specific statistics & it is often employed along with the Margin of Error. Confidence Interval = Mean of Sample ± Critical Factor × Standard Deviation of Sample. . Here, we see that the claimed or assumed value has to be equal to or nearly equal to the actual data for the null hypothesis to be true.
Null Hypothesis Examples
Now let us apply the null hypothesis to a few examples.
In an industrial study, it was claimed that on average production of 100 goods, the chance of encountering a faulty product was only 1.5 %. But during the study of a sample taken, it was found that the chances of encountering a faulty product were actually 1.55%. Comment on this condition.
In the case of the Null-Hypothesis Testing, the original claim is assumed to be correct. Here, it is assumed only 1.5 % of 100 goods were faulty products.
In this case, deviation helps ascertain the level of significance.
Calculation of Deviation Rate can be done as follows:
= (1.55%-1.50%) * 100/1.50%
Therefore, the Deviation Rate will be:
Deviation Rate = 3.33%
In this example, the standard deviationStandard DeviationStandard deviation (SD) is a popular statistical tool represented by the Greek letter 'σ' to measure the variation or dispersion of a set of data values relative to its mean (average), thus interpreting the data's reliability. from the assumed parameter is 3.33 %, which falls within the acceptable range, i.e., 1% to 5%. Thus, the null hypothesis can be accepted even when the actual valuation differs from the assumption. But if such deviation exceeds 5%, the hypothesis will be rejected. Beyond that percentage, the assumption made will have no justification.
There are many ways to verify a presumed statement. For example, with null assumptions, the mean of the sample is compared to the population meanPopulation MeanThe population mean is the mean or average of all values in the given population and is calculated by the sum of all values in population denoted by the summation of X divided by the number of values in population which is denoted by N.. Here, the term ‘mean’ could be defined as the average value of the parameter and the number of variables.
While we conduct various statistical tests like P-valueP-valueP-Value, or Probability Value, is the deciding factor on the null hypothesis for the probability of an assumed result to be true, being accepted or rejected, & acceptance of an alternative result in case of the assumed results rejection. , the results can be analyzed by determining the null-hypothesis and alternative hypothesis. Some of the reasons for its importance are discussed below:
- Logic Behind Statistical Significance Testing: Statistics is used to test if the assumptions occur by chance or for particular reasons. It helps in ruling out random factors causing an observation.
- Prove or Disprove Relational Statement: Null-hypothesis proves that there is no relation between two variables; thus, it is used for relational inference.
- Facilitates Alternate Hypothesis Testing: The alternate hypothesis is just one side of the coin. The null-hypothesis is essential for finding and validating its result.
- Confidence Interval: It reflects the same underlying statistical reasoning as P-value in excelP-value In ExcelP-value is used in correlation and regression analysis in Excel to determine whether the result obtained is feasible or not and which data set from the result to work with. It's value ranges from 0 to 1..
- Applicable in Different Fields of Study: Whether research, science, psychology, statistics, or investment, everything requires hypothesis testing
The null-hypothesis is based on analysis; therefore, interpretation is critical. Unfortunately, it can be easily misinterpreted and manipulated. In most cases, the significance testing is usually conducted to get rejected; thus, the results often come out false.
Another significant issue is selecting an appropriate sample sizeSample SizeThe sample size formula depicts the relevant population range on which an experiment or survey is conducted. It is measured using the population size, the critical value of normal distribution at the required confidence level, sample proportion and margin of error. for finding the probability or mean. A small sample size fails to provide accurate results. Similarly, a huge sample complicates the calculation.
Null Hypothesis vs. Alternate Hypothesis
Null-hypothesis refers to a statistical approach where the sample value deems to be the same as the population data. In this condition, their statistical significance lies somewhere within the confidence level. In contrast, for an alternate hypothesis, the sample value differs from the population data. In such a case, the statistical significance of these two values does not fall within the confidence level.
The null-hypothesis signifies the possibility of observations being caused by chance or random factors. In contrast, the alternate hypothesis highlights that the observations were caused by specific reasons.
Frequently Asked Questions (FAQs)
The null-hypothesis validates sample data being equivalent to the population data. This means that these two values have no statistical significance. One example is that a doctor states that a human being takes five days on average to recover from viral fever. Based on 50 patients, the average recovery rate is 4.97 days, which is approximately equal to 5 days. Thus, the null assumption is valid. The sample was taken from various states.
The null-hypothesis is accepted when the sample value is equal to or almost identical to the population data. In such a case, the statistical significance falls within the given cut-off confidence interval. Conversely, if the sample data is not equal to the population data or if the statistical significance level is below the confidence interval, the hypothesis is rejected.
Hypothesis testing is essential for the validation of sample data concerning population data. Moreover, it helps draw a meaningful conclusion in medical science, research, psychology, and statistics.
This has been a guide to the What is Null-Hypothesis and its Definition. Here we discuss null-hypothesis’ significance, formulas, and calculations using examples. You can learn more about statistics & excel modeling from the following articles –