Question

1) The average breaking strength of steel rod is specified
to be 18.5 thousand pounds. To test this a sa
sample
of 14 rods was tested. The mean and so obtained
were 17.85 and 1955 respectively. Is the result
of the experiment significant?​

Answer 1

Answer:

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Answer 2

Answer:

The average breaking strength of steel rods is 18.5.

Step-by-step explanation:

Given n = 14, σ = 1.955, x bar = 17.85, μ = 18.5, α = 0.05

Hypothesis is :

$H_{0}$ : μ = 18.5 vs $H_{1}$ : μ≠ 18.5

Ζ = (Χbar - μ)/(σ|√n) = (17.85 - 18.5)/(1.955|√14|) = $\frac{17.85-18.5}{1.955|\sqrt{14}| }$ = -1.244

P- value at 0.05 and Z = 1.244 corresponds to 0.2135

Therefore, 2P (Z < -1.244) = 2 × 0.10749 = 0.2150

P- value = 0.2150

Since P-value (0.2150) > 0.05

we failed to reject $H_{0}$

Hence,  it is clear that the average breaking strength of steel rods is 18.5.

Your question is incomplete, most probably your question is:

" The average breaking strength of steel rod is specified to be 18.5 thousand pounds. For this a sample of 14 rods was tested. The mean and standard deviation obtained were 17.85 and 1.955 respectively. Test the significance of the deviation by using 5% level of significance. "