<u>Answer</u>:
The null hypothesis: the mean egg thickness is 0.2 mm
The alternative hypothesis: the mean egg thickness is less than 0.2 mm
In statistics, the null hypothesis states that there is no significant difference between the observed value and the mean thickness. The alternative hypothesis states is the opposite and states the scientist's "idea" behind the experiment. Here, it refers to the fact that due to DDT, the egg shell will be thinner compared to the mean value.