Apply Logic and Evidence to a Scientific Explanation

What is empirical evidence?

evidence that’s been collected during an experiment (through observations and measurements)

What are variables?

The conditions in an experiment that may be changed or manipulated

What is a placebo? What variable can it be used as in an experiment?

A substance with no medicinal effect; control variable

What is an independent variable?

The condition that is manipulated or changed in an experiment

What is a controlled variable?

The condition that is kept the same in an experiment

Why do scientists repeat experiments?

To confirm results and have confidence in the data before drawing conclusions

What is needed before drawing a valid scientific conclusion?

Large amounts of reproducible data showing consistent trends and patterns

How are scientific conclusions often presented?

As cause-and-effect relationships

Do peer-reviews occur after an experiment is published or before?

before (but ofc after the experiment is over)

What is bias in an experiment?

When experimenters or subjects unintentionally influence the results

How can bias be reduced in an experiment?

By using a placebo, so neither experimenters nor subjects know who received the real treatment

What is a controlled setting?

An experimental design where only one variable is changed at a time

What factors help evaluate the strength of evidence? (4)

Bias, controlled setting, accurate data collection, and replicable results

Why are larger sample sizes and repeated trials important?

They provide more confidence in the evidence collected

Why must controlled variables be kept the same across trials?

So the experimenter can be confident the results were caused by the variable being tested

What is magnitude?

The size of an event/object/process

Why do different objects require different units of measurement?

Because their scale differs greatly ^{(from micrometers for hair to kilometers for distances)}

What unit measures the diameter of human hair?

Micrometers (μm)

What unit is commonly used to measure human height?

Meters

What unit measures the mass of atoms?

Atomic mass units

What unit measures the mass of an elephant?

Kilograms

What is a causal relationship?

relationship between two or more variables where one relationship causes change in an other (typically shows correlation)

Give an example of a causal relationship.

Smoking and emphysema; high blood pressure and vascular disease; or alcohol during pregnancy and fetal alcohol syndrome

Besides cause and effect, what else must be determined when analyzing a process?

The sequence of events

What do scietific experiments do?

test hypotheses

What is a quantitative observation?

study that gathers numerical data

Correlation means…

two or more things move/change together (but it doesn’t mean one causes the other)

Correlation means

a statistical relationship between variables where a change in one is associated with a change in another.

Is this correlation or causation?

In the same year that an area’s drinking water was contaminated by a chicken farm, the rate of stomach cancer in that area increased 3%. Based on this, we conclude that the contaminated water caused stomach cancer to increase.

Correlation (could be other variables that caused increase in stomach cancer)

Is this correlation or causation?

Victoria notices that every time she turns on the stove burner underneath a pot with water in it, the water boils. Victoria realizes that putting heat under water causes it to boil.

causation

Is this correlation or causation?

We saw that the thunderstorm that day caused rain in all the neighborhoods in the East Village. The power outage in West Village must have been because of the storm.

correlation (just bc there was a thunderstorm in east village doesn’t mean that’s why west village power went out)

Is this correlation or causation?

Hector learned in school that when tectonic plates shift, it cuases earthquakes to happen. There had been many earthquakes when Hector lived in California, and now he knew that the shifting of plates was what caused them.

causation (shifting of plates = earthquakes)