"You are testing to see if a new brand of fertilizer works better than the old brand. You have 20 plants and have divided them into two groups. The first will be grown with the old brand and the second will be grown with the new brand of fertilizer. You keep the water, temperature, light, etc. the same for both groups of plants and they are grown together in the same greenhouse. You measure the height in centimeters that the plants grow after a two week period."
What is your null hypothesis?
Would "The plants grown with the new brand of fertilizer would grow at the same or lower rate as the plants grown with the old brand." work?