The probability that the average length of a randomly selected bundle of steel rods is less than 124.5-cm i.e.,
P(M < 124.5-cm) is 0.0603..
We have Given that,
The lengths of the steel rods are Normally distributed.
mean of distribution (μ) = 125.2
standard deviation (σ) = 2.3
Sample size (n) = 25
Standard error = σ/√n = 2.3 /√25 = 0.46
convert to P(z < ???) using transformation to z-statistic which is N(0,1):
P(z < (M - population mean)/(standard deviation/square root(sample size))
P(M < 124.5 ) = P[(M - μ ) /σ /√n < ( 124.5 - 125.2 ) /0.46 ]
= P( z < -1.522 )
Using z table,
= 0.0603
Probability = 0.0603
Hence, the Z-score is -1.52 and the required probability is 0.0603
For more information about Probability of normal distribution, refer:
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