Stat. Steps to Determine if Data is Exponential - Cooney

1. graph x and y

2. ratio test
• copy L2 into L3
• copy L2 into L4
• delete first number of L3
• delete last number of L4
• L5 = L3/L4
• common ration = mean of L5 (1-var stat. of L5)

3. graph x, logy
• clear L3, L4, L5
• L3 = log(L2)
• check to see if transformed data is linear… must be on statement of proof: “The transformed data appears to be (roughly/strongly/etc.) linear. Therefore the original data is exponential.”
• graph L1, L3

4. calculate linear regression of x and logy
• (y hat) = a + bx
• (stat  calc  8  L1, L3, Y1)
• put line on graph (step 3)

5. residual plot to determine if truly linear (graph x, resid)
• resid: 2nd  stat  8

6. pattern or not (random scatter = equally spread above and below line)
• write sentence: “If the residual plot shows random scatter, then the transformed data is linear and therefore the original data is exponential.”

7. write equation log(y hat) = a + bx
• simply write equation from step 4 and put “log” in front of (y hat)

8. inverse transformation
• write in exponential form
• (y hat) = 10 (to the) [a + bx] (power)

9. predict


**reference information from problem!**