Question

Ms. Blankenship’s tenth grade class is studying the impact of photoperiod on plant growth. Her students fill 100 paper cups with potting soil and a single pea seed. Each cup is randomly assigned to one of four growth chambers. Each of the four growth chambers has an identical artificial light source (25 watts) but each has a different light (L) : dark cycle (D). Chamber 1 is set to 24L : 0D. Chamber 2 is set to 16L : 8D. Chamber 3 is set to 12L : 12D. Chamber 4 is set to 8L : 16D. Chamber 5 is set to 0L : 24D. All cups receive 5 ml of water, twice a week for three weeks. After 3 weeks, the height of each pea plant is measured to the nearest 00.0 cm.

The independent variable is photoperiod and is categorical with five levels (24:0, 16:8, 12:12, 8:16, 0:24). The dependent variable is pea height in cm and is continuous. The observations are unpaired and independent of one another.

Class Data for the Impact of Photoperiod on Seed Germination

24L : 0D	16L : 8D	12L : 12D	8L : 16D	0L : 24D
8.0	8.3	8.4	8.2	8.0
8.3	9.4	11.3	9.5	8.1
10.0	10.0	10.8	10.4	10.2
9.2	9.2	9.5	9.2	9.1
8.4	8.4	11.3	8.9	8.0
9.7	10.2	12.4	10.1	7.0
8.3	8.0	8.8	8.0	8.4
10.2	10.3	10.1	10.7	10.2
9.0	9.5	9.9	9.8	9.4
7.0	9.1	9.4	8.0	7.3
8.4	8.3	11.6	10.3	9.9
9.5	10.2	10.3	9.2	10.7
7.5	8.1	10.7	9.9	8.5
12.2	12.3	12.4	12.2	12.1
10.1	10.8	10.9	10.7	10.0
7.0	10.1	9.2	9.0	10.2
8.0	9.8	10.6	8.9	9.3
9.7	9.1	9.1	9.7	9.1
8.9	8.9	10.3	9.3	7.1

1. Which of these pairs of photoperiod treatments are significantly different?
   1. 24L : 0D vs. 0L : 24L
   2. 16L : 8D vs. 8L : 16D
   3. 12L : 12D vs. 24L : 0D
   4. 24L : 0D vs. 16L : 8D

Answer 1

As per the question asked the answer should be c. 12L : 12D vs. 24L : 0D as these two photoperiod are significantly different.