Nature of Science - Target 16

Nature of Science - Target 16

by KELLY COOTS

​VALID

​sound; just; well-founded

​REPLICATE

​to repeat, duplicate, or reproduce, especially for experimental purposes

Multiple Choice

A student completes an investigation, and claims that a 4‐inch pot that is painted purple will produce taller plants that a 4‐inch pot that is not painted. No other student is able to replicate her investigation and find the same evidence. This shows that the first student’s investigation was NOT

• an investigation

• able to be done by anyone else

• was actually done by anyone else

• valid

​What is Validity?

Reliability means that the same thing is done the same way, every time. Validity means that what is being done is actually right. Repeated trials make sure that an investigation is reliable: the same investigation was done the same, many times.​

Multiple Choice

Reliability means that the same thing is done 

• a different way

• many ways

• the same way

• opposite

​But what if the materials in the investigation weren’t the right materials to being with?

Let’s look closely at our wheatgrass investigation. Each trial was supposed to use 20 ml wheatgrass seeds, 1 four inch potting cup, and potting mix. If all of the students in your class all used the same materials, and followed the same procedures, then those repeated trials will be reliable.​

​But what if potting mix wasn’t used, and someone substituted soil from the ground out the classroom?

​That investigation concluded that wheatgrass won’t grow. But those results aren’t valid: something in the investigation was changed, making the results not usable.

Multiple Choice

Why was this conclusion not valid?

• it did not have a hypothesis

• something in the investigation was changed

• the potting mix was expired

• the soil was just mud

​What if the original directions were wrong to begin with? What if the directions simply said “soil?”

​Everyone doing the investigation would have used whatever soil they could find: this would not be a valid investigation.

​When other scientists repeat an investigation, the results they get should be replicated: they should get the same results as the original investigation. If they get the same results, the investigation is valid. If the results they get are different from the original investigation, then something has gone wrong. Scientists will check each other’s work to make sure that investigations are reliable and valid. If investigations are not reliable and valid, then the conclusions reached by the original investigation might be tossed out.

Multiple Choice

When other scientists repeat an investigation, if they get the same results, then the investigation is ____________.

• valid

• not valid

Multiple Choice

Scientists will check each other's work to make sure investigations are ________________________.

• correct.

• reliable and valid

• wrong

• unreliable and not valid

​The next time you see the moon, think about Galileo. Think about the first time that someone saw mountains on the moon, and conclude the moon was a sphere. Anyone who looks at the moon through a telescope, repeating Galileo’s investigation, would replicate his evidence: they would see the same mountains Galileo saw. The investigation can be repeated, the investigation is reliable, and the results of the investigation will be replicated by everyone who looks at the moon through a telescope. Galileo’s evidence is valid, and his conclusions can be trusted.

Multiple Choice

A reliable investigation means that the steps can be followed by another investigator. A valid investigation means that:

• the investigation was good science

• the investigation was not good science

• the investigation cannot be completed by anyone else

• the investigation should never have been done in the first place

Multiple Choice

to repeat, duplicate, or reproduce, especially for experimental purposes

• replicate

• valid

Multiple Choice

​sound; just; well-founded

• valid

• replicate