An economist studying inflation in electricity prices in 2018 and 2019 believes that the average price of electricity, even after adjusting for inflation, changed between these two years. To test his claim, he samples 9 different counties and records the average price of electricity in each county from each year. He then adjusts the prices for inflation. His results are given in the following table. Test the economist's claim at the 0.05 level of significance assuming that the population distribution of the paired differences is approximately normal. Let d = (prices in 2019)-(prices in 2018). Average Residential Retail Prices of Electricity ($/kWh) 2018 2019 18.79 17.31 14.39 12.89 17.72 18.25 14.56 12.64 16.16 14.23 14.25 12.57 18.51 16.69 12.54 13.06 16.35 15.87 Copy Data Step 2 of 3: Compute the value of the test statistic. Round your answer to three decimal places.