Statisticshard · Past Paper
If the combined mean of two groups is 40, Group 1 has mean 35 (n=30), and Group 2 has mean 43, find the number of observations in Group 2.
A40
B50
C60
D70
✓ Correct Answer: B — 50
40 = (30*35 + n2*43) / (30 + n2) => 1200 + 40n2 = 1050 + 43n2 => 150 = 3n2 => n2 = 50.
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