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 she will get fat If ___________________________ then _________________________

Try to use INCREASE and DECREASE in your hypothesis! 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

Use this hypothesis to identify the variables: 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: lights on DV: electric bill will be high

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

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: temperature DV: rottenness of milk

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. Independent Variable-different aged students Dependent Variable-time to finish puzzle   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-sizes of nails Dependent Variable-number of paper clips picked up    Egg Example The higher the temperature of water, the faster an egg will boil. Independent Variable-temperature of water Dependent Variable-time for egg to boil Depth Example The temperature of water was measured at different depths of a pond. Independent Variable-depth of pond Dependent Variable-temperature

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

Two 10th grade students wanted to know the effect of shoe brand on speed. They took 2 brands of track shoes (Nike and Adidas) and measured 50-yard dash times in each brand of shoe. They thought that the Nike shoes would be faster. They compared the dash times to see which shoe resulted in the lowest sprint times.   1. Independent variable: type of shoe Dependent variable: time to run 50-yard dash 2. Hypothesis: If I wear Nike track shoes, then I will decrease my time for the 50-yard dash

Laura loved to chew gum– and she especially liked to blow bubbles Laura loved to chew gum– and she especially liked to blow bubbles. She wondered if the type of sweetener (real sugar or artificial sweetener) affected the size of the bubble. She assumed that they would be the same size. Laura got a pack of regular gum and a pack of sugar-free gum and chewed each. She blew the largest possible bubbles for each type of gum– then she measured the size of the bubbles to see if the sweetener type made a difference.   1. Independent variable: type of sweetener Dependent variable: size of bubble 2. Hypothesis: If I chew gum with artificial sweetener,, then it will not effect the size of the bubble I can blow.

“I want to see if different colors of light help plants grow better “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? Color of light What is the dependent variable? Height of plant What are the constants? 1. amount of water 2. time watered 3. type of plant What is the control? Plant grown in white light

“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? Taping/non-taping of thumbs What is the dependent variable? time What are the constants? 1. same person 2. same shirt What is the control? Time with thumbs not taped

“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? Milk drank or not What is the dependent variable? Amount of food eaten at dinner What are the constants? 1. same food 2. same time 3. same people What is the control? Amount eaten when milk is not drank before dinner