Statistical methods

a$.$ A toxicity test is conducted with $4$ discrete concentrations of a toxicant. The numbers of daphnia in each concentration that die and that survive $($discrete outcomes$)$ are recorded. What statistical method should be used to analyze the data?

b$.4.$ A lake has $2$ major tributary streams. Average nutrient concentrations are recorded in each stream. What statistical methods should be used to compare the mean concentrations if the means are normally distributed?

c$.$ Temperature and annual precipitation are measured in a city over $50$ years. The data are found not to be normally distributed. What statistical method should be used to assess whether warmer temperatures are associated with higher precipitation?