Is net wt of corn flake packets still normal (µ=520 gm, σ=10 gm)?
Is a sample mean wt of 529 gm from 10 packets consistent with µ = 520 gm?
In this simulation, the null hypothesis is that the 10 packets are sampled from a normal (520, 10) population:
Click Accumulate and simulate selection and weighing of 10 corn flake packets from this population between 100 and 200 times. (Hold down the Simulate button.)
A mean weight of 10 packets that is 9 or more grams from the target of 520 gm would be very unlikely if the packing machine was working to specifications, so there is strong evidence that µ is not 520 gm.
Emphasise the general concepts:
This example is artificial.