RESEARCH METHODOLOGY

Detailed explanation-1: -In most large data sets (assuming a normal distribution of data), 99.7% of values lie between-3 and 3 standard deviations, 95% between-2 and 2 standard deviations, and 68% between-1 and 1 standard deviations.

Detailed explanation-2: -A positive z-score says the data point is above average. A negative z-score says the data point is below average. A z-score close to 0 says the data point is close to average. A data point can be considered unusual if its z-score is above 3 or below −3 .

Detailed explanation-3: -The mean of the standard normal distribution is 0. Z scores above the mean are positive and Z scores below the mean are negative. Once you have computed a Z-score, you can look up the probability in a table for the standard normal distribution or you can use the pnorm() function in R.