Objectivity, Accuracy and Precision Lesson Presentation in Pink and Green Photographic Style.pptx

ACCURACY AND PRECISION

1. ACCURACY AND PRECISION

2. QUICK STARTER: EVALUATE THIS Alvin and Sarah wanted to see whether water temperature affects how quickly salt dissolves, so they used warm water for one test and cold for another. They didn't measure the water temperature; they just guessed by feeling. In groups, suggest ways Alvin and Sarah can improve their experiment next time.

3. MARK SCHEME: ALVIN AND SARAH'S EXPERIMENT 1 mark: Did they identify a variable to test (water temperature)? 1 mark: Did they mention using different water temperatures (warm and cold)? 1 mark: Did they mention controlling any other variables (e.g., amount of water, amount of salt, stirring)? 1 mark: Did they describe how they measured how quickly the salt dissolved (e.g., time taken for all salt to disappear)? 1 mark: Did they mention measuring the water temperature accurately (not by feeling)? 1 mark: Did they acknowledge any problems that might arise from not measuring the water temperature accurately (e.g., the results might not be reliable)? 1 mark: Would their experiment allow them to draw a valid conclusion about the effect of water temperature on dissolving salt? Explain why or why not (based on the fairness of the test). Total Marks: 7 marks Additional Notes: Award marks based on the clarity and completeness of the student's explanations. If a student identifies a way to improve the experiment (e.g., using a thermometer), award an extra mark for their scientific thinking

4. Recognise bias Describe how to collect confident results. Explain the best way to replicate results. Objectives: WHAT ARE WE LEARNING?

5. In science, we must try to ensure our personal biases or preferences do not influence the outcome of our experiments. Paying attention to accuracy, precision, repeatability, and reproducibility allows us to trust that our findings are reliable and that the same results can be achieved under similar conditions. INTRODUCTION

6. This means gathering useful evidence without letting our wishes or guesses affect the facts. When we set up our experiments, we need to make sure we are not accidentally making it easier for the result we want to happen. For example, when testing if plants grow better with music, we should not give the "music plants" more water or sunlight than the quiet ones. AVOIDING BIAS

7. Ate Cookie Height (cm) Yes 49.1 No 48.00 Bias can be introduced further in the way we interpret evidence or data. For example, we hypothesise that eating cookies makes people jump higher. We might round up or round down data to support our hypothesis. We may cheer whenever someone who ate a cookie jumps, which also affects results. BIAS IN DATA

8. Accuracy refers to how close a measured value is to the true value or standard. This can be achieved by using the best equipment with the most appropriate scale for measurements. When measuring around your head, it is better to use a flexible measuring tape than a wooden metre stick. ACCURACY

9. Precision is about being able to repeat measurements and get identical or similar results each time. To achieve precision it is best to use consistent measurement techniques and the same apparatus throughout an experiment. You could get the same results each time but they may not be near the true value. PRECISION For example, when a liquid is placed in a container, it forms a curve called the meniscus. The water level should be read form the bottom of the meniscus each time the reading is taken to make readings precise. Top of meniscus Bottom of meniscus

10. This is the ability to repeat the experiment and get consistent results under the same conditions and by the same observer. To make experiments more repeatable, it is important to write up a detailed scientific method. It is also important to make sure the relevant variables are controlled and apply the same conditions to all subjects or samples. REPEATABILITY

11. This is the ability to replicate results under different conditions, by different observers or with different equipment. To make results more reproducible, it is important to share raw data and findings openly, allowing others to analyse the data themselves. Use standardised reporting techniques so evidence can be universally understood. REPRODUCIBILITY