(null hypothesis): Mean of the concrete drying time for both the amount of concrete and water are equal.
paraphrase it
The null hypothesis states that the average time it takes for concrete to dry is the same for different amounts of concrete and water used.
The null hypothesis states that the average drying time of concrete is the same for different amounts of concrete and water.
The null hypothesis states that the average drying time for concrete is the same regardless of the amount of concrete and water used.
