Statistics – Statistical Significance

Statistical Significance signifies that result of a statistical experiment or testing is not occurring randomly and is attributable to certain cause. Statistical significance of a result could be strong or weak and it is very important for sectors, which are heavily dependent on research works like insurance, pharma, finance, physics and so.

Statistical Significance helps in choosing the sample data so that one can judge the result or outcome of testing to be realistic and not be caused by a random cause.

Statisticians generally formulates the degree of statistical significance by sampling error. Generally, sampling error of 5% is acceptable. Sample size is also important, as it should be representative sample instead of very large sample considering the fact that large samples are prone to errors.

Significance Level

A level at which an event is considered to be statistical significant is termed as significance level. Statisticians uses a test statistic called p-value to get the statistical significance. If p-value of an event falls below a particular level then the event is considered as statistical significant. P-value is function of standard deviations and means of data samples. P-value is the probability of an event, which certifies that result of statistical testing is occurring by chance, or due to some sampling error. In other words, it is the risk of failure of a statistical test. Opposite of p-value is confidence level, which is 1 – p-value.

If p-value of a result is 10% then that means CL of the result is 90% Z-value = 1.645

If p-value of a result is 5% then that means CL of the result is 95% Z-value = 1.960

If p-value of a result is 2% then that means CL of the result is 98% Z-value = 2.33

If p-value of a result is 1% then that means CL of the result is 99% Z-value = 2.58

An example of findings reported with p values are below:

Statement: Drug 23 reduced patients’ symptoms compared to Drug 22. Patients who received Drug 23 (n=100) were 2.1 times less likely than patients who received Drug 22 (n = 100) to experience symptoms of Disease A, p<0.05.

Or

Statement: Individuals who were prescribed Drug 23 experienced fewer symptoms (M = 1.3, SD = 0.7) compared to individuals who were prescribed Drug 22 (M = 5.3, SD = 1.9). This finding was statistically significant, p= 0.02.

Dhasaratharaman

Mr. T. Dhasaratharaman

Statistician

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