Data point and data sets meaning

A data set is n pairs of X-values and Y-values. A data point is a single X-value and its corresponding Y-value.

I think you need to purchase a book on introductory statistics!

But.... in the attached file, a fictional scenario:

Column A represents the dose of a drug given to 17 different people, at 3 different doses (1, 2 & 3).

Column B represents, say, the concentration of the drug in blood 2 hr later.

The whole lot is a data set. Each coloured section is a subset of the data, corresponding to an individual dose. Any individual row is a data point (one person and their result).

You can see from the graph that there is a clear relationship between dose and effect. The response is NOT the same for all individuals at each dose. there is variability. That is measured by the standard deviation (SD) in column H. By statistical definition, 68% of values should fall within 1 Standard Deviation of the average value (above or below the average).

The graph plots the response (Y-axis) against the dose (X-axis). the dotted line represnts the line-of-best-fit to the data. The equation describing the line is
y = 75.398x - 34.172

r2 is a measure of variability. the closer r2 is to 1.0 the closer the relationship between effect (Y) and dose (X). In this case the 0.9448 means that 94.48% of the variability in the Y values is caused by the dose of the drug (X-values). the remaining 5.something % is caused by something else.... the day of the week, the time of the day... anything.