Science Forums 2

[CraigD]

I’m uncertain what the proposed experiment is.

In the first part of post number one, the linked to article states

The first part she heated to boiling in a pan on the stove, and the second part she heated to boiling in a microwave. Then after cooling she used the water to water two identical plants to see if there would be any difference in the growth between the normal boiled water and the water boiled in a microwave.

Later, is prescribes

Plant some seeds in 2 pots. Water one with the cooled water that was microwaved and one that's from the tap.

Which does not mention boiling water on a stove.

The experimental procedure needs to be better defined, and blinded.

Here’s a draft experimental design:

1. A person (Alice) places about a quantity of of water in a pot.
2. On a stove, Alice boils the water for about 2 minutes, then allows it to cool.
3. Alice places half the water in microwavable containers.
4. Alice boils the the water in the continers in a microwave overn for about 2 minutes, then allows it to cool.
5. Alice decants the water into several identical containers, discarding excess not-microwaved water so that there are equal amount of both kinds of water, and group the two kinds in separate areas on the work table.
6. Alice label the 2 areas with 2 random 2 digit numbers (drawn blind from a “hat”).
7. Alice notes on a single piece of paper which number is for the microwaved water, seals the paper in an envelope, and places it in a secure place (that Bob can’t see).
8. A person (Bob) not involved in the preparation, who doesn’t know which collection of containers contains the microwaved and not-microwaved water, labels the 2 kinds of water with 2 random 2 digit numbers.
9. Bob notes on a single piece of paper which of the container label numbers goes with which of the area labels numbers, seals it in an envelope, and places it in a secure place (that Alice can’t see).
10. Following package instructions, Alice plants seeds from the same packet in separate identical pots.
11. Alice labels each pot with the numbers from the water containers
12. Following package instructions, Alice waters each with identical amounts and following identical schedules, using water from the container with matching the pot’s label.
13. When the water is used up, Alice notes on a piece of paper the label number of the plant that appears healthiest, or notes that she can detect no difference.
14. If no difference is detected, the experiment is over, with a null result.
15. Alice and bob retrieve and compare their pieces of paper, and determine which of the 2 kinds of water was used to water the healthier and less healthy plant.

As many as possible of the experiments should be run in parallel.

Without blinding, the experiment is not valid, as the expectation of the experimenter may effect how she cares for the plants.