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Railways NTPC (Technical Ability) Metrology and Inspection Question Bank Metrology and Inspection

  • question_answer
    The management is interested to know the percentage of idle time of an equipment. The trial study should that percentage of idle time would be 20%. The number of random observations necessary for 95% level of confidence and + 5% accuracy is:

    A) 6400                

    B) 1600

    C) 460                              

    D) 160

    Correct Answer: A

    Solution :

    \[{{S}_{p}}=K\sqrt{\frac{(1-p)}{N}}\] \[0.05\times 0.2=2\sqrt{\frac{0.2\times 0.8}{N}}\] \[N=6400\]


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