hypotheisis

Question 1

Scientists investigated the use of bacteriophages to treat lung infections caused by bacteria. They infected the lungs of mice with a pathogenic species of bacterium. The mice were then divided into two groups, A and B.

*   The mice in group A were not treated with bacteriophage.

*   The mice in group B were treated by breathing in a spray containing bacteriophage particles.

After 3 days, the scientists killed the mice and removed their lungs. They washed out each set of lungs with a set volume of liquid. The scientists determined the number of live bacteria in the liquid.

The graph below shows the scientists’ results. The graph shows the mean and the range of the data about the mean for each group. Standard deviations of the means are not shown.

What would the scientists’ null hypothesis be for this investigation?

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Answer 1

The bacteriophage makes no difference to the number of (living) bacteria / there will be no difference in the number of (live) bacteria in treated and untreated mice / there will be no difference in the number of (live) bacteria in A and B;

Ignore no difference between mice