Resistors are electronic circuits that are manufactured on a high-speed automated machine. One of the key measurements is its resistance. To set up the machine and develop control charts, we measured 4 randomly selected resistors at 5 time periods (samples) over a day. (Details shown in the table below)

Time period X1 X2 X3 X41101099198598629959961009994399010031015100841015102010099985101310191005993

I calculated the Grand Mean as 1002.7 ohms.

What is the probability that the resistance of one electronic circuit produced is lower than 1000 ohms?

Can you explain this problem?

Thank you.