A student measuring the diameter of a pencil of circular cross-section

Question:

A student measuring the diameter of a pencil of circular cross-section with the help of a vernier scale records the following four readings $5.50 \mathrm{~mm}, 5.55 \mathrm{~mm}, 5.45 \mathrm{~mm} ; 5.65 \mathrm{~mm}$. The average of these four readings is $5.5375 \mathrm{~mm}$ and the standard deviation of the data is $0.07395 \mathrm{~mm}$. The average diameter of the pencil should therefore be recorded as :

  1. $(5.5375 \pm 0.0739) \mathrm{mm}$

  2. $(5.538 \pm 0.074) \mathrm{mm}$

  3. $(5.54 \pm 0.07) \mathrm{mm}$

  4. $(5.5375 \pm 0.0740) \mathrm{mm}$


Correct Option: , 3

Solution:

Use significant figures. Answer must be upto three significant figures.

Ans. (3)

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