Question

A study was conducted to determine the effectiveness of varying amounts of vitamin C in reducing the number of common colds. A survey of 450 people provided the following information:

Daily amount of vitamin C taken
None 500 mg 1000 mg
No Colds 57 26 17
At least one cold 223 84 43


What conclusion can be made? (1 point)
The data proves that vitamin C reduces the number of common colds.
The data proves that vitamin C has no effect on the number of common colds.
There appears to be an association between consumption of vitamin C and the increase of common colds.
There appears to be no association between consumption of vitamin C and the occurrence of common colds.
Since common colds are caused by viruses, there is no reason to conclude that vitamin C could have any effect.

Answer 1

Use the Chi-square (X^2) method.

X^2 = ∑ (O-E)^2/E, where O = observed frequency and E = expected frequency.

∑ = sum of all the cells.

E = (column total * row total)/grand total

df = n - 1, where n = number of cells

Look up value in X^2 table in the back of your textbook to come to your decision.