Statistics & Controlled Experiments

Some researchers are developing a new fertilizer designed to improve the growth of plants in hot, dry climates. The fertilizer was applied to one hundred desert plants in a greenhouse. The average daytime temperature in the greenhouse was 90°F, and the humidity levels were low. Which is best for the researchers to do next?

A compare plants that received fertilizer to similar plants that received none.

Used to determine the precision and confidence in the mean value and usually given as +/- 2 SE (How well does the mean sample represent the true mean of the population).

Standard Error of the Mean.

What does a large standard deviation indicate?

The data are spread widely around the mean.

"No Overlap" means...

There is a significant difference between two groups.

Erin is testing to see how different amounts of nitrogen infused in the soil will impact the height of her corn plants. She puts two corn plants into two pots. One is filled with nitrogen infused soil and the other is not. She puts the regular soil pot outside and the nitrogen infused plant in her bathroom. The corn in the regular soil grows to 7 feet tall and the corn in the nitrogen soil grows to 2 feet tall. What is her independent variable?

Nitrogen infused soil.

The null and alternative hypothesis can be the same.

No

Which option best describes the purpose of a scatter plot?

A graph that shows a possible correlation between two sets of data.

This is used for comparison in an experiment.

Control

In the memory drug that was referenced in the last question, a new drug is tested against an old drug. In this case, the old drug would be considered a ___________ because it is what is already used and you want to see if your drug is better than the old drug.

Negative control.

A bar graph is used for…

comparing distinct categories.

Giving a person a placebo treatment is when you give them a sugar pill or inject them with a saline solution that is not a real drug. When this is given to a patient in a study, it is not a real treatment, so it would be considered a…

negative control.

The hypothesis that states there is no significant difference between treatments would be considered a ___ hypothesis.

null

If error bars overlap, the difference _____ significant.

is not.

Which of the following is the best null hypothesis?

If flowers are grown in the presence of different fertilizers, then there will be no significant difference in flower height.

The parts of the experiment that remain the same for the control and experimental group are called _____.

constants

Lou wants to know if a new dental snack for dogs helps dogs maintain healthy teeth. In this experiment, two groups of dogs are monitored. The first group of dogs ate their normal food and received no snacks. The second group of dogs ate their normal food and received a snack prescribed by dentists to help with dental health. The third group of dogs ate their normal food and also ate the new dental snack. Group 1, the group of dogs who ate their normal food and received no snacks, serve what purpose in this experiment?

This is the positive control group, which shows a baseline to be used for comparison.

Lou wants to know if a new dental snack for dogs helps dogs maintain healthy teeth. In this experiment, two groups of dogs are monitored. The first group of dogs ate their normal food and received no snacks. The second group of dogs ate their normal food and received a snack prescribed by dentists to help with dental health. The third group of dogs ate their normal food and also ate the new dental snack. Which group represents a positive control group?

Group 2.

To test the effect of hormones on plant growth, 6 potted plant seedlings of the same species were measured and then sprayed with auxin (a growth hormone). After 4 weeks of growth under ideal conditions, the plants were measured again. To set up a proper control for this experiment, the investigator should.

grow another 6 seedlings of the same species under the same conditions, spraying them with distilled water only.

What is the hypothesis that states there is no significant difference between treatments, with any observed difference being due to chance?

Null hypothesis.

In order to assess significance in data based on error bars, which of the following should be used to calculate the error bars?

+/- 2 * standard error of the mean.

A _____ hypothesis suggests a potential result that a researcher expects.

alternative

Erin is testing to see how different amounts of nitrogen infused in the soil will impact the height of her corn plants. She puts two corn plants into two pots. One is filled with nitrogen infused soil and the other is not. She puts the regular soil pot outside and the nitrogen infused plant in her bathroom. The corn in the regular soil grows to 7 feet tall and the corn in the nitrogen soil grows to 2 feet tall. What is the dependent variable?

The height of the plants.

We are testing if Jazz music helps you sleep longer. We will have 2 groups sleep, 1 with jazz and 1 without. Which one is the experimental group?

The group listening to the music while sleeping.

A line graph is used.

to show trends over time or changes in related variables.

This symbol denotes the null hypothesis.

H0

In a controlled experiment, this group does not receive the what it being tested or a substitute. The results from this group are likely to show the baseline or normal response to the experimental conditions. This group is a _____ control group.

negative

Erin is testing to see how different amounts of nitrogen infused in the soil will impact the height of her corn plants. She puts two corn plants into two pots. One is filled with nitrogen infused soil and the other is not. She puts the regular soil pot outside and the nitrogen infused plant in her bathroom. The corn in the regular soil grows to 7 feet tall and the corn in the nitrogen soil grows to 2 feet tall. Which part of the experiment did she mess up on?

She does not have proper constants.

The ______ variable in an experiment is the one being deliberately changed or tested by the scientist.

independent

This symbol denotes the alternative hypothesis.

H1