If the graph is linear, use "Trendline" to plot the best fit line and have the equation of the line as well as R² on the graph. Record the slope (in unit) and y-intercept (in unit). Use Linest function and 90% reference data to calculate the uncertainty of the slope and y-intercept.
a. Use Excel's "Insert" tab to add a trendline to the graph, and then display the equation of the line and R² value on the graph. Record the slope and y-intercept.

b. Use the Linest function in Excel to calculate the slope and y-intercept of the best fit line. Then, use the "Analysis ToolPak" to calculate the uncertainty of the slope and y-intercept at a 90% confidence level.

c. Manually calculate the slope and y-intercept of the best fit line using the least squares method, and then use statistical methods to calculate the uncertainty of the slope and y-intercept at a 90% confidence level.

d. Use a statistical software package, such as SPSS or R, to perform linear regression analysis and calculate the slope and y-intercept of the best fit line, along with their uncertainties at a 90% confidence level. Then, plot the graph with the trendline and display the equation of the line and R² value.