A study compared three different display panels for use by air traffic controllers. Each display panel was tested in a simulated emergency condition; 12 highly trained air traffic controllers took part in the study. Four controllers were randomly assigned to each display panel. The time (in seconds) needed to stabilize the emergency condition was recorded. The results of the study are given in the following table. Let μA, μB, and μCrepresent the mean times to stabilize the emergency condition when using display panels A, B, and C, repsectively. The faster the resolution of the emergency condition, the better.

A        B         C

21       24       40

27       21       36

24       18       25       

26       19       32

Write the null hypothesis:


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