There is no bold portion in the sentence you gave
I would add some kind of punctuation between you and said.
I will prepare an excellent meal for you. Said the cook.
Answer: No, his experiment is not designed correctly.
Explanation: He didn't use the same measurements in each experiment. He should've either buried them all in the yard, or she should've kept them all in pots. Not having them in the same environment could affect the results of his experiment, thus making it inaccurate.