in a statistacal book following problem has been mentioned with solution:
In a nutritional study, 13 children were given a usual diet plus Vitamin A and D tablets. While the second comparable group of 12 children was taking the usual diet. After 12 months, the gain in weight in pounds was noted as given in the table. Can you say that vitamin A and D were responsible for this difference.
A=5,3,4,3,2,6,3,2,3,6,7,5,3
B=1,3,2,4,2,1,3,4,3,2,2,3,-
SOLUTION:
Null Hypothesis: Vitamin A and D are responsible for the gain weight difference
Alternative Hypothesis: Vitamins are not responsible for the gain weight difference
my question is:
the assumed hypothesis (Null and Alternative as mentioned) seems to be wrong. i think just opposite should be assumed.
please give expert views.
thanks
Firstly, I think Vitamins cannot be responsible of a gain of weight, but they can contribute to this gain.
Yes, the null and alternative hypothesis are wrong. Null hypothesis always states no difference in the treatment groups. I however feel that Vitamin D and A cannot be directly associated with weight gain. The null hypothesis can therefore be that
there is no difference in weight gain of children consuming vitamin A and D tables vs controls
Alternative: Weight gain is higher in the children consuming vitamin A and D tables than control
It seems after one year of supplement there was significant improvement among subjects received VA, VD and foods. But your sample size was too small and the study seems non-blinded in nature, so probably the treatment group received more attention, as a result their macronutrient intake may be increased. So, in a table compare the characteristics of the participants at baseline and during the study, before making a conclusion.
A hypothesis is a speculation or theory, based on insufficient evidence that lends itself to further testing and experimentation. With further testing, a hypothesis can usually be proven true or false. A null hypothesis is a hypothesis that says there is no statistical significance between the two variables.
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