Exposure to different light wavelengths may affect the spawning rate in zebrafish. So, an experiment is conducted where one group of 50 zebrafish is exposed to blue light, and their spawning rate is compared with the control group having the same sample size. To test the claim, we begin with the null hypothesis that the mean spawning rate in the exposed and the control group is the same and an alternative hypothesis that the blue light increases the mean spawning rate. The experiment showed that the mean spawning rate in the exposed group was 550 per fish, whereas, for the control group, it was 250. Calculating the test statistic from these data requires prior knowledge of population standard deviation, which is 146, known from the previous studies. Using these data, we can calculate the z statistic and observe that it falls in the critical region at the significance level of 0.05. Additionally, the P-value for this z statistic is less than 0.05, concluding that the blue light enhances the spawning rate in zebrafish.