Part CCSIR NET December 2023pooled-variance-formula

Pooled variance formula

Two groups $G_{1}$ and $G_{2}$ have 10 and 30 patients with mean diastolic blood pressures 80 and 100 mmHg and variances 4 and 2 mmHg $^{2}$ . Let ${\bar{X}}, S^{2}, C$ and R be the mean, variance (with divisor n), coefficient of variation (%) and range of the combined group. Which of the following statements are true?

A.X̄ = 95✓ Correct
B. $S^{2} = 77$
C.C > 180/19
D.R > 8✓ Correct

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward, and why this one tests execution slip.

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50 are analysed free — try those first.

The trap it tests

Execution slip

The idea was right. The computation was not.

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Pooled variance formula

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