Observation vs. Inference

Review - Observation What is an observation? – Using your five senses to take note of and observe your surroundings

Inference An inference is when you make an assumption or prediction about something that you observe After you make an observation, you usually make an inference about what is going on

Let’s practice making inferences! The next three slides show some fossil imprints that were found during a archeological dig. We’re going to record some observations and then make some inferences about what may have happened millions of years ago….

What do you think happened? In your notebook, please write a story (around ½ page – be DETAILED please) describing what you think happened to the creatures in our fossil evidence please complete the ‘Inference’ portion of your worksheet

P. 4 “Hypothesis, Variables, Constants, Controls”

Hypothesis Hypothesis: an educated guess or prediction; an “if, then” statement If ____ independent variable ______ then__ dependent variable _______

Example: Independent Variable: I feed my cat a lot of food Dependent Variable she will get fat If ___________________________ then _________________________

Remember Try to use INCREASE and DECREASE in your hypothesis! Ex. IF I increase the amount of food I give my cat, THEN she will increase her weight

Use the following statements and write a good hypothesis – think about how one thing will affect the other and use your ‘if, then’ statements. Try using the words “increase” and “decrease” 1) Chocolate may cause pimples. 2) Salt in soil may affect plant growth. 3) Bacterial growth may be affected by temperature. 4) Sunlight may cause skin cancer. 5) Temperature may cause leaves to change color. 6) Amount of reading that you do may affect your intelligence.

Types of Variables There are 2 main types of variables: Independent Variable: The variable that is changed by the scientist; the ‘I control’ variable Dependent Variable: The variable that might change because of what the scientist changes – what is being measured

Your hypothesis can TELL you what your variables are! Ex. If I drink Mountain Dew before bed, then I will not sleep very much. IV: Drinking Mountain Dew DV: the amount of sleep

Practice Use this hypothesis to identify the variables: If I leave all the lights on all day, then my electric bill will be expensive IV: ______________________ DV: ______________________

If I brush my cat more, then there will be less fur on my furniture IV: ______________________ DV: ______________________

Now read the following experiment and identify the independent and dependent variables Elizabeth wanted to test if temperature affected how fast milk goes bad and curdles. She left milk in a room temperature closet, a fridge, and a oven that was turned on low heat. She then measured how rotten the milk was after 10 days. IV: ____________________________________ DV: ____________________________________

Variable Practice Puzzle Example Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle. Identify the variables in this investigation: Independent Variable Dependent Variable Electromagnetic Example An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured. Independent Variable Dependent Variable Egg Example The higher the temperature of water, the faster an egg will boil. Independent Variable Dependent Variable Depth Example The temperature of water was measured at different depths of a pond. Independent Variable Dependent Variable

Constant Constant: something that scientist makes sure is the same throughout the experiment Ex. Watering the plants the same amount of water or making sure you are testing the same person every time

Control Control: The part of the experiment that the scientist doesn’t change or add the variable to Ex. The plant with the white light

“I want to see if different colors of light help plants grow better. I am going to take four plants (all the same type) and set them up underneath different lights. One will be a white light, one will be red, one will be blue, and one will be green. Everyday, I will water them the same amount at the same time. I will also record how high each plant grows for two weeks and then look at my results.” What is the independent variable? What is the dependent variable? What are the constants? What is the control?

“I want to see how taping my thumbs will affect my time it takes to button up a shirt. I will test the same person – they will do three trials buttoning up the same shirt with their thumbs taped to their palms. Then I will do three trials where their thumbs are not taped up. I will average the time in seconds that it takes to button up and shirt with their thumbs taped and without their thumbs taped.” What is the independent Variable? What is the dependent variable? What are the constants? What is the control?

“I want to see if there if drinking a lot of milk will affect how much you eat at dinner. I will take 5 people. For three days, I will give them two glasses of milk to drink before they eat dinner. I will serve the same food for those three days and they will eat at the same time every day. After three days of drinking milk, I will then have the people eat for three days without drinking milk before they eat dinner (again, same food, same time). I will measure how much food they eat in the three days that they drink milk and the three days that they don’t drink milk and compare my results.” What is the independent variable? What is the dependent variable? What are the constants? What is the control?