A study examined the effect of protein consumption on weight gain in rats. Investigators obtained 14 female rats and randomly assigned 7 of them to a low-protein diet and the other 7 in a high-protein diet. After 60 days, the weight gained by each rat was recorded (in grams). Here are the summary findings, displayed as "mean (standard deviation)":
$$\begin{array}{l}
\begin{array} { l l }
\text { Low-Protein Diet}&\text { High-Protein Diet}\
101.3(20.6)&127.5(21.1)
\end{array}
\end{array}$$ Researchers want to know if the amount of protein in the rats' diet significantly affects their weight gain.
What should they conclude at significance level 5%?

Question

A study examined the effect of protein consumption on weight gain in rats. Investigators obtained 14 female rats and randomly assigned 7 of them to a low-protein diet and the other 7 in a high-protein diet. After 60 days, the weight gained by each rat was recorded (in grams). Here are the summary findings, displayed as "mean (standard deviation)":
$$\begin{array}{l}
\begin{array} { l  l  } 
\text { Low-Protein Diet}&\text { High-Protein Diet}\
101.3(20.6)&127.5(21.1)
\end{array}
\end{array}$$ Researchers want to know if the amount of protein in the rats' diet significantly affects their weight gain.
What should they conclude at significance level 5%?

Quizplus · Accepted Answer

The data shows a difference in mean weight gain between the two groups, suggesting that protein intake may affect weight gain. Rejecting the null hypothesis (which typically states there is no effect or difference) is appropriate when observed differences are unlikely to have occurred by chance alone, as implied by the provided data.