Question

Plants in space

Even in times of a tight budget, mankind’s dream to reach out further into the universe and send manned spacecrafts to more distant planets is alive and kicking. Among the problems that will need to be addressed before this dream can become a reality is the question of how to supply a spacecraft with sufficient amounts of food for a space mission that ranges from months to years.

As part of these efforts, a subcontractor for the national space agency, "Martian Green Thumbs", is looking into ways to stock spacecraft with enclosed environments in which fresh plants can be grown. The effect of air pressure changes, gravity, various temperatures, as well as the artificial light conditions in outer space are tested on a variety of plants to establish ideal growth conditions and hardiness of plant varieties.

Recently, Dr. Marla Brown, a researcher at this company, studied the feasibility of growing a particular variety of a nutritious green plant in energy-efficient environments. Dr. Brown systemically varied the light intensity of the light bulbs that illuminated the beds in which the plants would grow on board a spacecraft or space station.

She created three test plant beds that could hold up to 20 plants each. She could only get small plant donations from any one nursery, so 20 plants came from each of three different nurseries. To make it easier, each nursery was assigned to one of the three test beds. The first batch that was grown, batch A, was placed in a closed environment illuminated at an intensity of 25 watts, for the duration of one week. The second batch, B, was placed into the environment next, and was illuminated at an intensity of 35 watts for one week. Finally, the control batch C was grown. It was placed in direct sunlight outside for one week. Lighting for all three batches simulated earth conditions with sprouts being illuminated from daybreak until dusk. During the study, a few plants died. From batch A, 25% of the plants were lost, and 20% of the plants in batch B died.

Dr. Brown measured the growth of the remaining plants to determine ideal light conditions. Her results indicated that growth was stronger in batch B than in batch A, with a representative subset of batch B sprouts being 0.1 inch longer. Also, Dr. Brown noticed that growth in batch B and batch C did not differ, suggesting that the 35 watt environment may be an adequate simulation of earth lighting. Follow-up studies are being conducted at present.

Which of the following are true (there may be more than 1):

- Poor or missing comparison group

- No Random assignment

- DV could be more sensitive, accurate, or precise

- DV is not scored objectively

- DV is not valid

- subject/participant bias

- mortality or attrition

- small sample size

- poor sample selection

- experimenter bias

- premature generalization of results

- confuse correlation with causation

Answer 1

The following are true with regard to the experiment:

- No Random assignment.

The sample from each three nursery were assigned into three different groups for different treatments. Instead, if the plants were randomly grouped and classified and were given the different treatments, then this study would have been more valid and reliable. As, plants from different nurseries means their may be some sort of difference in conditions in which they have grown, and this confounding factor is a threat to the internal validity of the study.

- Small sample size.

The size of the sample needed to larger,which means there could have been more plants in each groups.

_ Premature generalization of results.

The confounding variables were not taken into account which could alter the results, before reaching the generalization of results.