A toy factory makes 5,000 teddy bears per day. The supervisor randomly selects 10 teddy bears from all 5,000 teddy bears and uses this sample to estimate the mean weight of teddy bears and the sample standard deviation. How many degrees of freedom are there in the estimate of the standard deviation?
DF = n - 1
DF = 10 - 1
DF = 9
DF = n - 1
DF = 10 - 1
DF = 9