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-1.5
Step-by-step explanation:
When population standard deviation is known, then the formula to find the z-test statistic for population mean is given by :-
, where n= Sample size.
= Population mean
= Sample mean
= Population standard deviation.
As per given , we have (average infants contracted typhoid each month)
n= 4 (No. of months)
Then , the value of the appropriate test statistic will be :
Hence, the value of the test statistic = -1.5
Step-by-step explanation: