What is the sample size?

Question

A team of researchers observed that the acorn density of the oak forests in New York fluctuates from year to year and that mice populations in the forest were increased when the acorn density was high (Jones, Ostfeld and Wolff, 1996). These researchers asked, "If there are more acorns and mice in the forest, will there be a higher density of ticks that carry Lyme Disease?" They hypothesized that the number of ticks carrying Lyme disease would be high when acorn density in the forest was high.
To test their hypothesis, the researchers studied six unfenced oak forest plots in New York. Mice were initially removed from each plot by trapping. Four tons of acorns were added to three of the plots (with the help of some local girl scouts!). The remaining three plots did not receive acorns. Ticks were collected in 225 sections (15m X 30m) in each plot, and were identified and counted. The number of mice in each plot was counted also.
I get that the dependent variable is: the number of mice and ticks?

I am really lost on determining the level of treatment and number of replicates? Any help is appreciated. Would the number of replicates be three or six in this case?
How can you tell what the sample size is in an experiment like this?

Answer 1

In this experiment, it seems there are two levels of treatment: plots with added acorns (treatment group) and plots without added acorns (control group). Therefore, the level of treatment is two.

The number of replicates is determined by the number of independent experimental units exposed to each level of treatment. In this case, there are three plots with added acorns and three plots without added acorns. Each of these six plots serves as a replicate for its respective treatment condition. So, the number of replicates is six.

The sample size is the total number of individual observations or data points. In this experiment, the sample size would depend on the number of sections (15m X 30m) in each plot where ticks were collected. Since ticks were collected in 225 sections in each of the six plots, the total sample size would be 225 sections x 6 plots, which equals 1,350 sections. This represents the total number of data points collected for the study.

In summary:

Level of Treatment: 2 (plots with added acorns and plots without added acorns)

Number of Replicates: 6 (three plots for each treatment)

Sample Size: 1,350 sections (225 sections per plot, six plots)