Answer:
4.20
Step-by-step explanation:
Given data:
the average increase in sales 'x' = 18
ad campaign will increase sales for a fast-food chain 'μ'= 15
standard deviation 'σ'= 5
random sample of stores 'n'=49
In order to determine z-value, we use the formula i.e
z=( x-μ ) / (σ/ )
z=( 18-15) / (5/ )
z= 3/ 0.714
z= 4.20