# What's the diff between a z-score, t-score and a P value?

Nov 25, 2017

Explanation and Difference

#### Explanation:

Z Score- tells you how many standard deviations from the mean your result is.
If z-score is +ve, it indicates that the score is above the mean and if it's -ve it indicates the score is below the population mean and if it's 0 it indicates the score is same as the population mean.
Z score is used when: the data follows a normal distribution, when you know the standard deviation of the population and your sample size is above 30.

T-Score - is used when you have a smaller sample <30 and you have an unknown population standard deviation.
Like z-score, t-scores are also a conversion of individual scores into a standard form

p-value is the probability that your null hypothesis will be rejected. The experimenter sets the level of significance and when the p-value < significance level, the null hypothesis is rejected.

So z-scores and t-scores measure the significant difference between the population means whereas p-value just gives us a result to reject or not to reject our null hypothesis that we set, it doesn't give you the statistic.

Hope this helps :)