1. Statistics: Hypothesis Testing Q

I'm confused on how I should go about creating the hypothesis for the population. Lets say there are n = 5 people and they are tested to see how long their nails are. These values are z scores (I made these values up and it's in cm): 1.30, 2.25, 2.60, 1.10, and 3.05. My z-critical will be p<0.05 on a two tail.

By this data, I reject the null hypothesis because most of them are above 1.96. But how would I do this calculation using the formula:
mean - hypothesized population mean / standard error?

I don't understand how to obtain the mean, standard deviation, and I'm not sure what I should hypothesize for the population mean. Someone please show me step by step on how to solve this. Thank you.

I'm confused on how I should go about creating the hypothesis for the population. Lets say there are n = 5 people and they are tested to see how long their nails are. These values are z scores (I made these values up and it's in cm): 1.30, 2.25, 2.60, 1.10, and 3.05. My z-critical will be p<0.05 on a two tail.

By this data, I reject the null hypothesis because most of them are above 1.96. But how would I do this calculation using the formula:
mean - hypothesized population mean / standard error?

I don't understand how to obtain the mean, standard deviation, and I'm not sure what I should hypothesize for the population mean. Someone please show me step by step on how to solve this. Thank you.