chi square distribution with df = n-1
Given that sample of size n=90 are randomly selected from the population of numbers (0 through 9) produced by a random-number generator
Since sample size is large and randomness is followed we can assume that the variable follows a normal distribution.
Hence the sample variance would follow a chi square distribution with degree of freedom =
This is because we have is standard normal hence square will be a chisquare variate. When we sum n variates we get chi square distribution with df n-1