Question: The California Lettuce Research board was originally formed as the Iceberg Lettuce Advisory Board in 1973. The primary function of the board is to fund research on iceberg and leaf lettuce. A recent project involved studying the effect of varying levels of sodium absorption ratios (SAR) on the yield of head lettuce. The measurements (the number of lettuce heads from each plot) of the kind observed were as follows:

                   Lettuce type

SAR         Salinas         Sniper

3              104             109

5              160             163

7              142             146

10            133              156

a. Determine if the number of lettuce heads harvested for the two lettuce types is independent of the levels of sodium absorption ratios (SAR). Use a significance level of 0.025 and a p-value approach.

b. Which type of lettuce would you recommend?