An appliance manufacturer claims to have developed a new toaster oven that consumes an average of no more than 250 W. From previous studies, it is believed that power consumption for toaster ovens is normally distributed with a variance of 324 W. A consumer group suspects the actual average is more than 250 W. They take a sample of 20 toaster ovens and calculate the average consumption to be 260 W. What is the parameter of interest in this situation? And test the consumer group's suspicion at the 5% significance level.