# What is a P value and it's significance in hypothesis testing

#1

Hi,

I am facing a difficulty in understanding the P-value and it’s significance. Can some one please explain me what is p-value and it’s significance.

Also why we will reject the null hypothesis when P-value is <0.05?

#2
1. What is p-value?

You would have come across the term ‘p-value’ in hypothesis testing. You can have either null hypothesis or alternate hypothesis.The p-value is calculated, assuming the null hypothesis is true.

1. Significance of p-value?

p-value is used in hypothesis testing to support or reject the null hypothesis. If the p-value is less than a threshold value, you can reject the null hypothesis

1. Why reject null hypothesis for p-value < 0.05?

Generally we use 0.05 as threshold. So if the probability is less than 0.05, you can safely reject the null hypothesis in support of alternate hypothesis.

You can also refer this discussion thread:

#3

I will be using mean value in my example to explain p value.

Definition of p value: Given the null hypothesis is true (i.e. H0 is true), the probability that the sample mean is equal to population mean is known as p value.

For e.g. you are conducting a study on a sample and found that sample mean is 80. The probability that the population is also having a mean of 80 is denoted by p.
p < 0.05 signifies that the probability is very low and hence we can neglect null hypothesis.