1A2 Experimental Design Flashcards
Describe how Investigation design encompasses planning data collection, using precise measurements, analyzing errors, and interpreting data to draw conclusions and answer scientific questions.
Define:
standard units of measurement
An internationally recognized system for scientific measurements.
Also called SI Units, this common language consists of base units for different kinds of measurement.
For example, the base unit for length is the meter (m).
List out the 7 base units of the standard units of measurement.
- meter (m): length
- seconds (s): time
- kilogram (kg): mass
- Ampere (A): electrical current
- Kelvin (K): temperature
- mole (mol): amount of matter
- candela (Cd): luminosity
Additional SI units are generally combinations of a base unit and a prefix that indicates a magnitude of ten.
For example, a centimeter is 1/100th of a meter.
Why do scientists use standard units in scientific measurements?
To ensure consistency and global understanding.
Standard units allow scientists around the world to communicate findings clearly and consistently without the risk of misinterpretation due to unit differences.
For example, scientists worldwide use kilograms as a measurement of mass to avoid confusion when comparing data.
Define:
unit conversion
The process of converting a value in one unit to the same value, but in the form of another unit.
This involves mulitplying or dividing the original value by a conversion factor, or a pre-defined ratio that compares the two units of measurement.
For example, an American scientist may want to convert their data from meters to miles, since Americans are not as familiar with the length of a meter.
What are common errors in unit conversion?
- rounding errors
- incorrect conversion factors
- inconsistent units
Using consistent conversion factors ensures calculations align with scientific standards.
For example, using the wrong conversion factor when converting kilometers to miles will result in an incorrect answer.
What are significant figures?
The digits in a measurement that reflect its accuracy and precision.
Significant figures indicate the precision of a measurement, with more digits showing greater accuracy and detail.
What are the rules for determining significant figures?
- All non-zero digits are significant.
- All zeros in between non-zero digits are significant.
- All zeros before the first non-zero digit are NOT significant.
- All zeros to the right of non-zero digits with decimals are significant.
- All zeros after a non-zero non-decimal number are NOT significant.
These rules help determine how much precision is present in a measurement.
How do you round significant figures?
If the next digit is 5 or higher, round up.
For example, when rounding 3.456 to two significant figures, the third digit (6) is 5 or greater, so you round up the second digit (5) to 6, resulting in 3.5. Rounding ensures the result reflects the measurement’s precision.
How many significant figures are in the number 12,564,000?
5
Non-zero digits (1, 2, 5, 6, and 4) are significant, but trailing zeros are not unless there is a decimal (e.g., 12,564,000.0).
What is standard notation?
The most common way to express numbers.
Standard notation is used by most people when communicating the size of a number.
For example, 20,000 and 4,700,000 are written in standard notation.
What is scientific notation?
A way to express very large or small numbers using a coefficient and an exponent.
Scientific notation simplifies the writing of numbers that are too large or small to be practical for regular use.
Describe the format of scientific notation.
a x 10^x
a is a coefficient that has an absolute value between 1 and 10. x represents a power of ten, either negative or positive.
How do you convert a small number to scientific notation?
- Move the decimal to the right until the absolute value of the number is between 1 and 10.
- Count the number of places that the decimal moved.
- Use the negative value of the number from step 2 as the exponent in the power of ten.
Converting a small number to scientific notation results in a negative exponent. This represents the decimal moving to the right.
How do you convert a large number to scientific notation?
- Move the decimal to the left until the absolute value of the number is between 1 and 10.
- Count the number of places that the decimal moved.
- Use the positive value of the number from step 2 as the exponent in the power of ten.
Converting a large number to scientific notation results in a positive exponent. This represents the decimal moving to the left.
How do you convert from scientific notation to standard notation?
Remove the 10^x, then move the decimal x times to the right (if positive) or left (if negative).
Example: 2.304 x 10⁻⁷ becomes 0.0000002304. Moving the decimal to the left makes the number smaller.
How do you convert standard notation to scientific notation?
Move the decimal point to get a number between 1 and 10, then multiply by 10 raised to the appropriate power.
Example: 56,000,000 becomes 5.6 x 10⁷. The exponent represents how many places the decimal point was moved to the left.
What is accuracy?
The closeness of a measurement to the true value.
Accuracy ensures that measurements are correct and reflect real-world conditions.
What is precision?
The consistency of getting the same result multiple times.
High precision means measurements are consistent, even if they are far from the true value.
What is the difference between accuracy and precision?
- Accuracy refers to how close a measurement is to the true value.
- Precision refers to the consistency of measurements.
You can have high precision without accuracy and vice versa.
What does reliability in research describe?
The ability to repeat study results under the same conditions.
A study with high reliability produces consistent results each time, regardless of when or who conducts it.
How are reliability and validity different in research?
- Reliability refers to consistency.
- Validity refers to accuracy.
A study can be reliable without being valid, but if a study is valid, it is often reliable.
How many significant figures are in the number 12.0000?
6
The zeros after the decimal point are significant because they show the precision of the measurement.
How many significant figures are in the number 0.00004?
1
Only the non-zero digit (4) counts as significant. Leading zeros do not contribute to precision.
Define:
Random error
It refers to unpredictable variations in measurements that occur due to small, uncontrollable factors.
For example, if you’re measuring the length of an object with a ruler, slight differences in how you align the ruler each time could cause random errors in your measurements. Over time, this would lead to small fluctuations between trials.
How can errors be reduced?
- Increasing sample size
- Taking multiple measurements
- Calibrating equipment
- Using randomized samples
These strategies help minimize both random and systematic errors improving the overall reliability and validity of results.
What type of error causes predictable bias in measurements?
Systematic error
For example, a faulty scale always reading 2 kg heavier introduces bias.
A researcher observes that their data points cluster tightly together but are consistently far from the true value. What does this indicate?
High precision, low accuracy.
For instance, repeatedly measuring a length as 10.5cm when the true value is 12cm demonstrates precision without accuracy.
What visual aid is best for showing percentages in a dataset?
Pie chart
For example, a pie chart can represent how much sales have been made across different product categories in a month.
Fill in the blank.
Data presented in rows and columns is called a ______.
Table
Tables organize information into rows and columns, making it easier to read and compare data.
What graph best shows trends or patterns over time?
Line graph
Line graphs highlight trends, such as how temperature changes hourly or sales grow monthly.
Fill in the blanks.
In 2-dimensional plot, the x-axis runs ______ , while the y-axis runs ______ .
horizontally; vertically
The orientation of these axes helps in visualizing relationships between variables. For example, in a graph tracking speed, time (x-axis) influences speed (y-axis).
What role does proper calibration play in measurements?
It helps prevent systematic errors.
Regular calibration ensures measurement instruments stay accurate and provides consistency across different experiments.
When should you use a pie chart versus a bar graph?
- Pie charts for proportions.
- Bar graphs for comparisons.
Pie charts are best for showing proportions within a whole, while bar graphs are better for comparing individual values across categories.
How do you choose the best graph for your data?
- Line graphs to show trends.
- Bar graphs for comparisons.
- Pie charts for proportions.
For instance, you can use a line graph to track monthly revenue growth.
Why are axis labels important in graphs?
To clearly identify the variables being represented.
For instance, labeling the x-axis as “Time (hours)” and the y-axis as “Temperature (°C)” helps avoid misinterpretation.
True or False:
Tables are the best method for analyzing trends over time.
False
Line graphs are better for visualizing trends, like temperature changes over a week, while tables are used to display raw data.
What is the difference between qualitative and quantitative research?
- Qualitative research uses descriptive data.
- Quantitative research uses numerical data.
Qualitative research collects descriptive data through methods like interviews, observations, and case studies. For example, collecting stories from teachers about their career experiences to understand the challenges and rewards they encounter in the profession.
Quantitative research measures numerical data through experiments and surveys. For example, tracking test scores before and after implementing a new teaching method.
What is the dependent variable (DV) in an experiment?
The variable measured.
The dependent variable is the variable that you measure in the experiment to observe how it was affected by changes made to the independent variable.
If you change the temperature to see how it affects a liquid’s rate of evaporation, the rate of evaporation is the dependent variable.
What is the independent variable (IV) in an experiment?
The variable manipulated.
The independent variable is the variable that you manipulate to observe its effect on the dependent variable.
For example, if you change the temperature to see how it affects a liquid’s rate of evaporation, the temperature is the independent variable.
True or False:
A dependent variable changes in response to the independent variable.
True
For example, in an experiment testing fertilizer effects, plant growth (dependent) changes with the amount of fertilizer (independent).
What is a constant in an experiment?
A factor that remains unchanged throughout the experiment.
Constants are crucial for ensuring that any observed changes are due to the independent variable rather than other factors.
For example, in a plant growth experiment, the amount of water and soil type should remain constant.
What are confounding variables?
Unexpected factors that might influence the relationship between the independent and dependent variables.
Confounding variables can skew results if not controlled. For example, in a study about exercise and weight loss, diet would be a confounding variable if not controlled for.
Define:
control group
A group that does not receive the experimental treatment.
The main purpose is to provide a standard for comparison by not receiving the experimental treatment. This helps identify if changes in the experimental group are due to the treatment rather than other factors.
Why is random sampling important in research?
To reduce bias and improve the validity of results.
Random sampling ensures every individual in a population has an equal chance of being selected. For example, randomly selecting students from a school ensures fair representation in a survey on study habits, as it avoids over-representing or under-representing any specific group.
Fill in the blank.
In a study, researchers track the performance of two groups of employees—one that follows a new training program and another that doesn’t—and compare their productivity levels over three months. This is an example of a/an ______ study.
experimental
This represents an experimental study because the researchers actively manipulate one variable (the training program) to see its effect on the outcome (productivity).
Experimental studies are used to establish cause-and-effect relationships.
What is a positive correlation between two variables?
A relationship where as one variable increases, the other also increases.
For instance, the amount of study time and exam scores often show a positive correlation: studying more typically results in higher scores.
Fill in the blank.
Scientists are investigating the relationship between physical activity levels and stress reduction. They gather data by surveying a large group of people about their exercise habits and perceived stress levels over the past year without influencing their behavior. This is an example of a/an ____ study.
observational
This represents an observational study because the researchers passively observe and collect data on naturally occurring variables (dietary habits and heart health) without any manipulation.
Fill in the blank.
Predicting values within the range of observed data is called _______.
Interpolation
For example, estimating a temperature reading at 15°C when data is available for 10°C and 20°C.
What is extrapolation?
It is predicting values beyond the observed range.
For instance, using past population data to forecast future growth trends.
Why is it important to calculate percent error in an experiment?
To measure how accurate the results are compared to the expected value.
For example, if the expected value is 50g and the measured value is 48g, the percent error quantifies the deviation as 4%.
A scale consistently shows that an empty container has a mass of 5 grams. What must be done before adding anything to the container?
Calibrate the scale so that the container has a mass of 0 grams.
Otherwise, whatever you add to the container will register as 5 grams heavier than it truly is.
Calibration fixes systematic errors, ensuring accuracy for all subsequent measurements.
Fill in the blanks.
The range of a dataset represents the difference between the _______ and _______ values.
highest; lowest
The range provides a simple measure of data spread. For example, in the dataset [3, 7, 10, 15], the range is 15 - 3 = 12.
Fill in the blank.
Dimensional analysis ensures ____ _______.
unit consistency
For example, converting 5 km/h to m/s ensures accurate comparison of speeds across different units.
How do scientists draw conclusions from data?
By summarizing the evidence collecting and making a statement that confirms or refutes their hypothesis.
Scientists will look at the evidence that was collected, analyze patterns or trends, then compare to their original hypothesis. Then, scientists will make inferences in order to explain their results.
