Unit 1 – Lecture 2

Harold owns two hamsters – they live in separate cages, but they’re exactly the same in every other way [age, weight, cage design, etc]. Suddenly, the hamsters start gaining weight – but he has always fed them the same food [Food A] and has been feeding them the same amount. He decides to go to the store to check out new food options. A clerk at the store tells him that he’s heard of a different food, Food B, that causes less weight gain than the other foods. Harold thinks that the clerk might just be being sneaky to make a sale, so he talks to other people in the store – but they all say the same thing. He decides to purchase a small bag of Food B and test it on hamster #1 before he feeds it to his favorite hamster, #2 to see if food B will cause less weight gain. Based on talking to so many people, he thinks it probably will.

The Scientific Method a tool used to solve problems used by EVERYONE – not just scientists Steps in the Scientific Method develop Problem ……Statement collect Background …… Info form Hypothesis perform Experiment collect Data analyze Data form Conclusion Observe

Defining Variables Independent Variable [IV] changes the other variable [DV] “I control the IV” it is not changed by the other variable [it is INDEPENDENT of the DV] Dependent Variable [DV] is changed by the other variable [IV] [ it is DEPENDENT on the IV]

Defining Variables - Example Given the purpose statement below, what 2 things will you measure in your experiment? Purpose: to determine whether food B will cause less weight gain than food A [normal food] in a hamster when fed over a period of 2 weeks. Variable 1: TYPE of food --it is important to note that you are NOT measuring the impact of the food’s color, size, shape, or other characteristic. Variable 2: amount of weight gain

Defining Variables – cont’d The DV depends on the IV. I change the IV. Which of these sentences makes sense? The type of food fed to the hamster depends on the amount of weight the hamster gains. OR The amount of weight the hamster gains depends on the type of food fed to the hamster

Defining Variables – cont’d “The amount of weight the hamster gains depends on the type of food fed to the hamster.” IV = type of food [“I control the IV” !!!!!] DV = weight gain of hamster

Test Groups Two different groups in an experiment: Control Group - group that does not receive the treatment or change functions as a standard by which you can measure the results of your experiment we know that what we are testing is NOT affecting this group Hamster #2 being fed Food A [the “normal” food].

Test Groups – cont’d Two different groups in an experiment: Experimental Group – group in the experiment which receives the change/treatment what we are testing IS affecting this group Hamster #1 being fed Food B [the “new” food].

Constants Constant – something you want to remain the same throughout an experiment. Purpose: to figure out whether food B will cause less weight gain than food A [normal food] in a hamster when fed over a period of 2 weeks.

Discuss What things need to remain the same in order for you to be sure that ONLY the difference in type of food is causing the change in weight? Come up with a list of 5 or more things. What’s the Point? No Constants, No Confidence

Hypotheses Forming a Hypothesis If, Then format statement, NOT a question contains IV and DV predicts specific outcome of the experiment what type of change are you making? what type of change are do you predict you’ll see? abbreviation [used frequently] for change = Δ

Hypotheses – cont’d Types of Hypotheses Hypothesis – predicts change in the results between the control & experimental groups If [change] in IV, then [change] in DV Null Hypothesis - predicts no change in the results between the groups If change in IV, then NO CHANGE in DV.

Hypotheses – cont’d the POINT of the NULL hypothesis is to be rejected / disproven. it states that there’s no relationship between your variables.

Discuss Come up with a null hypothesis for each hypothesis below. [ states no change or no relationship between your variables]. Patients taking drug A for their headache will recover faster than patients taking a placebo. NULL: Patients taking drug A for their headache will recover in the same time as patients taking a placebo. [no change in recovery time] Tomato plants exhibit a higher rate of growth when planted in compost rather than in soil. NULL: Tomato plants show no difference in growth rates when planted in compost rather than soil. [no change in the growth rate]

Performing the Experiment As part of performing the experiment, the following must be completed: materials LIST for the experiment contains ALL equipment used in ALL groups contains how many of each item are used LIST of steps in your procedure be specific important – need to have repeatable results

Collecting Data Collecting data takes place during the experiment typically in a data table title of table contains IV and DV IV on left, DV on right finalized table has data in numeric order according to trial number OR in ascending order if there aren’t specific trials.

Analyzing Data Analyzing data takes place after the experiment. typically in graph form [IV on X-axis, DV on Y-axis] Comparing Qualitative & Quantitative Data types used: bar graph, pie chart qualitative data – data involving characteristics [qualities – color, type, etc.] quantitative data – numerical data [quantities]

Analyzing Data – cont’d Comparing two types of Quantitative Data scatter plot – line graph w/o the line line of best fit – drawn through the average of the plotted points line graph – connects the dots between sequential points

Question: What kind of graph should we use for our hamster experiment graph? variables: type of food, amount of weight gain

Conclusions Conclusions contain: a restatement of the purpose a description of data analysis a restatement of the hypothes(is/es) a statement of accepting or rejection of hypothesis & other stuff you’ll see on a rubric specific to each lab

Homework Complete pg 6 of your Unit Packet Simpsons & the Scientific Method w/s