Aresearcher is interested in whether the color of an animal's surroundings affects learning rate. she tests 16 rats in a box with colorful wallpaper. it is known that the average rat of this strain can learn to run this particular type of maze in a box without any special coloring in 25 trials, with a variance of 64; the distribution is normal. the mean number of trials to learn the maze for the rats tested with the colorful wallpaper is 11. what is the null hypothesis?