Astudent performed an experiment to see if water temperature affects the level of activity in aquatic snails. the student set up four tanks with five snails in each tank. all four of the setups were identical in every way, except for the temperature of the water. in order to make the conclusions more valid, the student could:
(1) alter the ph of the water
(2) change the size of the tank
(3) carry out the experiment for a shorter period of time
(4) use a larger number of snails

(4) use a larger number of snails

Explanation:

The size of sample selected from a population of interest during a research has effect on the accuracy/validity of the outcome of such research. The effect of sample size can be deduced from the formula for determining sample size to be selected during a research which is expressed below:

Where Z-score = confidence level

            SD = Pre-determined standard deviation

            ME = Margin of error.

The margin of error is inversely proportional to the sample size. Hence, the higher the sample size, the lower the error margin and vice versa.

The student could have increased the validity of the outcome of his research by using a larger number of snail samples in each of the tanks.

The correct option is option 4.

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