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A company has been producing steel tubes of mean inner diameter of 2 cm. A sample of 10 tubes gives an inner diameter of 2.01 cm and a variance of 0.0004 cm². The value of test statistic is :

Solution

Correct Option: 2

Given information:

  • Population mean (μ) = 2 cm
  • Sample size (n) = 10 tubes
  • Sample mean (x̄) = 2.01 cm
  • Sample variance (s²) = 0.0004 cm²

The sample standard deviation is needed for the test statistic formula.

s=s2s = \sqrt{s^2}

s=0.0004s = \sqrt{0.0004}

s=0.02s = 0.02 cm


For a small sample size without known population standard deviation, the t-test statistic is used:

t=xˉμs/nt = \frac{\bar{x} - \mu}{s/\sqrt{n}}

Substituting the values:

t=2.012.000.02/10t = \frac{2.01 - 2.00}{0.02/\sqrt{10}}

t=0.010.02/10t = \frac{0.01}{0.02/\sqrt{10}}

t=0.010.02/3.162t = \frac{0.01}{0.02/3.162}

t=0.010.006325t = \frac{0.01}{0.006325}

t=1.58t = 1.58

t1.5t \approx 1.5

Therefore, the value of the test statistic is 1.5.

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