The described situation requires inference about a mean or means. Identify the response variable and whether the setting involves a single sample, a matched pairs, or two independent samples. The physiological blind spot refers to a very small zone of functional blindness in the eye where the optic nerve passes through the retina. We do not notice it because our nervous system compensates for it. Can eye training reduce the size of a person's physiological blind spot? Researchers recruited a representative sample of adults with normal vision. Each participant performed training exercises with one eye for three weeks. The size of the physiological blind spot was measured (in degrees of visual angle squared) with a motion detection task both prior to training and again after the training was completed.

One sample of n people was taken and the physiological blind spot was measured. After that, the people selected underwent 3 weeks of eye training and their physiological blind spot was measured again. At the end of the experiment you have two sets of data for the sample, let's call X₁: physiological blind spot of one person before taking eye training", the measurements were taken before the training will correspond to this variable, and X₂: physiological blind spot of one person after three weeks of eye training" the second measurements correspond to this variable.

In this type of situation, where only one sample is taken and both variables are measured to the same observational unit (there is a pair of observations for each person), the observations are dependant and the corresponding test is the paired samples t-test.

To analyze the information you need to create a new variable, usually symbolized as Xd, that will be the difference between X₁ and X₂.

So your response variable would be

Xd: "Difference between a physiological blind spot of one person before taking eye training and physiological blind spot of after three weeks of eye training"

Xd= X₁ - X₂

The study parameter will be the mean of the variable "difference" μd.

I hope it helps!