For every opinion, belief, or point of view, there is someone who holds a different opinion, belief, or point of view. One of the interesting characteristics of humans is the diversity of opinion about the topics we cover. Our experience will be richer if we examine our perceptions and the evidence on which they are based.
What is the Point
A person often expresses belief as a fact that assumes proof and justifies a conclusion. In spite of the complexity of the belief, we can identify the points both made and implied by the statement and examine each individually. We will pick one of the points and treat it as a hypothesis, that is, a statement or explanation from which predictions can be made and tested. Next, we will write another hypothesis to represent a contrasting belief. One of these hypotheses will express the condition without an effect or a change or a difference, and we will call it the “null” hypothesis (null=no effect, no change, no difference). Then, based on predictions made from the hypotheses, we will describe the information we need to decide which belief is true that is, if the predictions are accurate.
Suppose that the hypothesis statement for the week is, “Aliens from another planet visited Earth. Life got its start here from the traces they left behind.”
Ideas Contained in the Statement
This statement contains three ideas: 1) aliens visited Earth; 2) aliens left traces; and, 3) life on Earth started from alien substances. There is a priority among these ideas in the order in which they should be considered. That is, aliens had to visit Earth before they could leave traces, and they had to leave traces before life could get a start from them.
Can we prove that aliens visited Earth? In other words, there is a hypothesis that aliens visited our planet. The contrasting hypothesis is that aliens have not been here. The latter hypothesis is called the null hypothesis because it states that aliens have not come here. It is called the “null hypothesis” because it says that the factor (aliens) we are trying to prove had an effect did not have that effect. That is, it contains the null element that the factor does not have an effect, exerts no influence, makes no difference.
In order to prove the alternative hypothesis that aliens have been here, we set out to reject the null hypothesis that they have not. If the alternative hypothesis is reasonable, then you should feel comfortable in accepting its conclusion if you obtain enough evidence to reject the null hypothesis. Other possible null hypotheses are, “There is no trace of a visit to Earth by aliens,” or “Life started spontaneously on Earth.” Note two aspects of this process. First, we justify our alternative hypothesis by proving that the null hypothesis is incorrect. Second, we advance our understanding only if the alternative hypothesis is a more accurate statement of the effect of the causal factor.
An essential characteristic of useful hypotheses is that they make predictions that can be tested with evidence (facts, data). If we hypothesize that aliens visited Earth, we can predict that they left some trace of their presence on the planet.
To discriminate between the null hypothesis and its alternative, we would need proof of an alien presence on our planet. Collect evidence that could reject the null hypothesis. (There is only one set of evidence since you are attempting to reject the null hypothesis, not prove each hypothesis separately.) Such evidence could include tissue that contains DNA different from DNA so far analyzed from species on Earth, technology that has not been invented yet on Earth, footprints that are uniquely different from any species past or present, or an alien.
There is a temptation to elaborate hypotheses to include additional ideas. For instance, “Aliens from a drying planet visited Earth in a desperate search for water.” Complicating your hypothesis makes it difficult to test the fundamental point that aliens paid a visit to Earth. Keep the hypothesis simple, test it, and, on the basis of the results of your first test, consider testing any of the other ideas with its own pair of hypotheses.
Submitting Hypotheses and Description of Evidence
The Hypothesis Activity
Click on the weekly module. Then click on the name of the assignment for the week that starts with an “H” and the number of the week, e.g. H01 for week#1. Download the attached file that contains a table with empty cells on the right where you fill in your answers that are indicated in the cells on the left. Read the statement for the week and list the number of ideas indicated. Write your answers using the causal factor in the table. The appropriate null hypothesis, alternative hypothesis, and description of the evidence needed to discriminate between the hypotheses might be:
NH: Aliens have not visited Earth.
AH: Aliens have visited Earth.
E: Discriminating evidence would be tissue that contains DNA different from DNA so far analyzed from species on Earth. The DNA from the many earth species that have been studied shows the same basic structure and genetic code (A, D, C, and T). A radically different genetic code would strongly suggest a different origin of the sample. You also need to describe how you would exclude confounding factors so that your interpretation of the evidence would not be compromised or challenged as inadequate. In this example, it would be necessary to state that you would take measures to avoid contamination of the DNA samples, and specifically, by airborne spores of earthly bacteria and fungi as well as cells from the persons collecting and processing the samples.
Attach the .rtf (rich text format) file containing your answers to the hypothesis activity assignment and submit it.
Grade and Feedback
Probably more than any other activity in this class, regularly dissecting statements, writing hypotheses, and testing predictions will give you the opportunity to hone your critical reading and critical thinking skills. Whenever you do not earn the full 5 points on a week’s class statement, we will provide you with comments specific to what you submitted to tell you what you should have done that week so that you can see how to do it correctly in the remaining weeks. Make a habit of checking the comments.