Microscope is a means and a way to collect data. Then by such means, you can think from the data itself to decide a problem.
Let's assume that you want to observe sperm. Let me help you raise "sperm watching" to a higher level of scientific research.
You should have glass slides, straws, small containers (Petri dishes), solution volumeter and other basic appliances.
What quantitative data can you get from sperm? Density-Dilute semen to a certain volume and suck a drop on the glass slide with a straw to count how many sperm there are. So how much is this dilution? You have to experiment many times to get the best method to a measurable level. Let's assume that if you find a way to dilute semen to 50 sperm per drop, then you can get a quantitative data by making slide at one time. After dilution, you should take multiple data and then average them to get an estimate of sperm density.
It is not easy to develop this method, and you may encounter many problems, such as, what concentration of saline, or pH, is used to ensure sperm activity? How to dye for better observation? If you swim too fast, how to slow them down? Would it be better to kill them and observe? . . .
OK, now that you have a standard method to obtain data, you can start designing experimental problems. At this time, you should have a record, write down the complete method of measuring sperm density, and use this method every time in the future. This is the most basic requirement of scientific research, "consistency".
Then you can ask, does drinking coke affect sperm density?
You, or your friends, are the experimental individuals. Then your experimental variable is that you drink n volumes of cola before taking semen vs. you don't drink cola.
Basic design: drink cola for 24 hours and take sperm density. After a period of time, find a day, do not drink, and take sperm density. Then compare the density and draw a conclusion.
Seems simple? So how do you control all other factors that may affect sperm density? This is actually very difficult. On the day of sampling, your behavior, diet, etc. must be consistent. That is to say, except for coke, everything else should be the same: eating, sleeping time, exercise time and things to do. Then these factors may be long-term. You have slept more this week, and you may have more sperm. In other words, your behavior should be consistent within one week before sampling.
So what you need to do is to investigate the literature first: what factors in human life will affect sperm quality? After you know it, you may want to keep these factors as consistent as possible within a certain period of time, such as a certain amount of sleep, a certain diet structure, a certain amount of tube stretching frequency, and a certain amount of exercise time ... All these variables should be recorded.
At this time, you find that your method is getting more and more perfect.
Then you can experiment and decide a date and time to take semen density. The time between your two samples may be one week or one month. In life, the week before sampling, the life schedule is consistent. The only difference is that before one of the samples, you drank n volumes of coke.
And then you get the data ... Not yet!
You think one experiment can explain the problem? No way. You have to repeat the experiment many times, get multiple sets of data, and then explain through statistical principles whether cola has an effect on sperm density. Statistics, you can ask me or Zhihu these predecessors who answered your questions, it is not difficult.
Then, at this time, it may have been half a year, and you finally got a conclusion. Then you have to go back, look at all the records, see if there are any mistakes or omissions, and do you want to redo them.
In fact, sperm density is not an ideal experimental point. I only know a little and do what I want. It may take a lifetime of struggle to achieve a job you like and a person with mobility. I wish you success.
