3.
A nutritionist wants to compare the proportion of people following two
different diets, Diet A and Diet B, who successfully lost weight. In a sample of 80
people following Diet A, 50 achieved weight loss. In a sample of 100 people
following Diet B, 60 achieved weight loss. The nutritionist will test if there is a
significant difference between the proportions at a 0.05 significance level.
Hypothesis:
H₀: There’s no significant difference in the proportions of weight loss success
between Diet A and Diet B. (p₁ = p₂)
H₁: There is significant difference in the proportions of weight loss success
between Diet A and Diet B. (p₁ ≠ p₂)
Level of significance: α=0.05
Test Statistic: Z-test
values are ±1.96. Since ∣0.34∣<1.96, we fail to reject the null hypothesis.
Critical Region: At a 0.05 significance level for a two-tailed test, the critical z-
Computation:
n1 = 80 x1 =50
n2 =100 x2 = 60
( p 1− p 2 )
z=
√ p 1(1− p 1) p 2(1− p 2)
n1
+
n2
( 0. 625−0.6 )
z=
√ 0. 625(1−0. 625) 0.6 (1−0. 6)
80
+
100
0. 025
z=
√ 0. 625( 0.375) 0. 6( 0. 4)
80
+
100
0. 025
z=
√ 0. 2344 0. 24
80
+
100
0.025
z=
√ 0.00293+ 0.00 24
0. 025
z=
0.0 730
z=0.34
Decision:
Since the calculated z-score (0.34) is less than the critical value of 1.96,
Therefore we fail to reject the null hypothesis.