Based on the experimental setup and procedures you've described, you would formulate your hypotheses to investigate the antimicrobial effect of different fruit extracts (from strawberry, citrus lemon, and green apple) against microorganisms, with chloramphenicol serving as a positive control and distilled water as a negative control.
Hypothesis
Null Hypothesis (H0): There is no significant difference in the zone of inhibition caused by the fruit extracts (strawberry, citrus lemon, green apple) when compared to the positive control (chloramphenicol). The extracts will show no antimicrobial activity against the microorganisms present in the agar.
Alternate Hypothesis (H1): At least one of the fruit extracts (strawberry, citrus lemon, or green apple) will demonstrate a significant zone of inhibition against the microorganisms, indicating antimicrobial activity, with some extracts potentially showing more activity than the positive control (chloramphenicol) and the negative control (distilled water) exhibiting no inhibition.
These hypotheses can then be tested statistically by measuring the zones of inhibition after the incubation period and comparing these measurements across the different segments of the petri dish.