In this experiment, a good hypothesis might be "If the fertilizer is applied as directed to tomato plants, the plants will produce larger fruits than when fertilizer is not applied". This experiment would actually not be as easy to do as it first sounds. Planting the plants in a garden would expose them to multiple variables that could affect the results. Hence, it would be best to use uniform 2 gallon pots, with all the same potting soil used in each, filled to the exact same level on the pots. Tomato seedlings of a single variety should be bought and planted in the exact same way, especially with regard to planting depth, one into each pot.

There should be at least 20 different pots set up, 10 as experimental plants, and 10 as controls. In the experimental plants, the fertilizer will be added as instructed by the manufacturer's label on the fertilizer. In the control plants, no fertilizer will be added. All plants need to be kept on a patio or deck and rotated as to their relative positions at least once a day so that no extra light or warmth is provided for any particular plants. All plants should be watered with the same amount of water each day. When the plants set fruit, they should be picked at the same time after first appearance of the fruit, probably 3 weeks. The time should be the same for each tomato picked. Each tomato should then be picked and its mass found as a way to determine its size objectively.

We would expect to find that the fertilized tomatoes will provide fruit that is slightly larger than the unfertilized tomatoes. In that case, the conclusion would be that the fertilizer if applied as done, results in fruit of a slightly larger size. We would also see other differences in the plants, although these are not the focus of the study and would not affect our conclusions about the size of the fruit. These differences would include rate of growth, size and number of leaves, strength of stems, time to start fruiting, and rate of growth of the fruit itself.