Blake's Mortgage Company utilizes four different appraisers for the purpose of determining the value of a house. There is a concern by the company's owner that the appraisers are not providing the same estimates. She wants to determine if there is a difference between the four appraisers. Six houses were selected and each appraiser provided an appraisal for each of the six houses. What would be the best statistical test to use for the analysis of this data?