Do various occupational groups differ in their diets? A British study of this qu

Question

Do various occupational groups differ in their diets? A British study of this question compared 90 drivers and 59 conductors of London double-decker buses. The conductors' jobs require more physical activity. The article reporting the study gives the data as "Mean daily consumption ± (se)." Some of the study results appear below.

What justifies the use of the pooled two-sample t test?

The similarity of the sample standard deviations suggests that the population standard deviations are likely to be similar.The similarity of the sample standard deviations suggests that the population standard deviations are likely to be different.    The similarity of the sample means suggests that the population standard deviations are likely to be similar.The similarity of the sample means suggests that the population standard deviations are likely to be different.

Is there significant evidence at the 5% level that conductors consume more calories per day than do drivers? Use the pooled two-sample t test to obtain the P-value. (Give answers to 3 decimal places.)

Drivers Conductors Total calories   2811 ± 40     2846 ± 49   Alcohol (grams) 0.21 ± 0.07 0.38 ± 0.14

Explanation / Answer

The similarity of the sample standard deviations suggests that the population standard deviations are likely to be similar.

Option A is correct.

The statistical software output for pooled t test is:

Two sample T hypothesis test:
1 : Mean of Population 1
2 : Mean of Population 2
1 - 2 : Difference between two means
H0 : 1 - 2 = 0
HA : 1 - 2 > 0
(with pooled variances)

Hypothesis test results:

Hence,

t = 4.773

df = 147

P - value = 0.000

Difference Sample Diff. Std. Err. DF T-Stat P-value 1 - 2 35 7.3324355 147 4.7733117 <0.0001

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