Question

One sample has a mean of M= 6, and a second sample has a mean of M = 12. The two samples are combined into a single set of scores. What is the mean for the combined set if both of the original samples have n = 4 scores? The new mean is What is the mean for the combined set if the first sample has n = 3 and the second sample has n = 6? The new mean is What is the mean for the combined set if the first sample has n = 6 and the second sample has n = 3?

Answer 1

Answer:

a) 9

b) 10

c) 8

Step-by-step explanation:

We are given the following in he question:

Mean of sample A = 6

Mean of sample B = 12

Formula:

$Mean = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}$

$\dfrac{\displaystyle\sum x_a}{n_a} = 6\\\\\dfrac{\displaystyle\sum x_b}{n_b} = 12$

a) original samples have n = 4 scores

$\dfrac{\displaystyle\sum x_a}{4} = 6,\sum x_a = 24\\\\\dfrac{\displaystyle\sum x_b}{4} = 12,\sum x_b = 48\\\\\text{Combined mean} = \displaystyle\frac{\sum x_a + \sum x_b}{4+4}=\frac{24 + 48}{4 + 4} = 9$

b) first sample has n = 3 and the second sample has n = 6

$\dfrac{\displaystyle\sum x_a}{3} = 6,\sum x_a = 18\\\\\dfrac{\displaystyle\sum x_b}{6} = 12,\sum x_b = 72\\\\\text{Combined mean} = \displaystyle\frac{\sum x_a + \sum x_b}{3+6}=\frac{18+72}{3+6} = 10$

c) first sample has n = 6 and the second sample has n = 3

$\dfrac{\displaystyle\sum x_a}{6} = 6,\sum x_a = 36\\\\\dfrac{\displaystyle\sum x_b}{3} = 12,\sum x_b = 36\\\\\text{Combined mean} = \displaystyle\frac{\sum x_a + \sum x_b}{6+3}=\frac{36+36}{6+3} = 8$