Experimental Design – Controls, Variables, Conclusions

DIRECTIONS: For each different scenario below, you will be asked to answer the questions using the phrases from the word bank. Attempt each scenario on your own. When you complete a scenario, STOP and wait for Mrs. Goodnight or Ms. Irish to check your work before you work on the next scenario.

SCENARIO 1 – Light and Plants

PICTURE 1PICTURE 2

WORD BANK
Growth of the plant Temperature Plant with light Plant without light
Using same plant breed Light present or not Measure leaves with ruler (cm)

HYPOTHESIS: If plants receive no light, then the plant will not grow, because plants need energy from light to grow.

  1. Which picture represents the control group when testing the hypothesis above? ______
  2. Which picture represents the experimental group when testing the hypothesis above? ______
  3. What is the manipulated variable (what is different in the pictures)? ______
  4. Give 2 controlled variables for this experiment (what is the same in the pictures? ______
  5. What is the responding variable? ______
  6. How will you measure the responding variable every week? ______
  7. From your prior knowledge, what do you think the conclusion of this experiment would be after 4 weeks of study? (Not in word bank.) ______

SCENARIO 2 – Melting Solids

Kaitlyn wants to find out which frozen solid melts the fastest: soda, ice, or orange juice. She pours each of the three liquids into the empty cubes of an ice tray, and then places the ice tray in the freezer over night. The next day, she pulls the ice tray out and sets each cube on its own plate. She then waits and watches for them to melt. When the last part of the frozen liquid melts, she records the time.

HYPOTHESIS: If Kaitlyn freezes soda, ice, and orange juice, then the orange juice will melt the fastest because orange juice has a lower melting point than soda and ice.

WORD BANK
Time the frozen liquid to melt Different types of liquids Orange juice Soda
Ice Timer/Stopwatch
  1. What is the control group when testing the hypothesis above? ______
  2. What are the experimental groups when testing the hypothesis above (there are two)? ______
  3. What is the manipulated variable? ______
  4. What is the responding variable? ______
  5. What would we use to measure the responding variable? ______
  6. Which liquid do you think will melt last; soda, water, or orange juice? (Answer not in word bank.) ______

SCENARIO 3 – Redwood Trees

Three redwood trees are kept at different humidity levels inside a greenhouse for 12 weeks. One tree is left outside in normal conditions. Height of the trees is measured once a week.

WORD BANK
Same tree breed 12 weeks timeframe Tree left outside in normal conditions
Measure with same instrument every time Redwood growth Different humidities
  1. What is the control group when testing the scenario above? ______
  2. What is the manipulated variable? ______
  3. What is the responding variable? ______
  4. List three controlled variables that would be used for the scenario above?
  5. ______
  6. ______
  7. ______

SCENARIO 4 – Goldfish Feedings

One tank of goldfish is fed normally (once a day), a second tank of goldfish is fed twice a day, and a third tank of goldfish is fed four times a day during a six week investigation. The fish’s body fat is recorded daily.

WORD BANK
Normally fed fish Goldfish fed twice a day Goldfish fed four times a day # of feeds a day
Six weeks timeframe All goldfish Same tank size Body fat differences
  1. What is the control group when testing the scenario above? ______
  2. What are the two experimental groups in the above scenario?
  3. ______
  4. ______
  5. What is the manipulated variable? ______
  6. What is the responding variable? ______
  7. List three controlled variables that would be used for the scenario above?
  8. ______
  9. ______
  10. ______
  11. List one more variable you would want to control in this experiment that is not already listed above. ______
  12. In the space below, reread Scenario 4, then draw and label what this experimental setup would look like (reference Scenario 1).