RB

Scientific Method and Metric System Review

Scientific Method

  • Definition of Science vs. Scientific Method

    • Science = knowledge about a subject

    • Scientific method = procedure for testing ideas via interrelated steps

  • Steps of the Scientific Method

    • Make observations

    • Ask questions

    • Develop a hypothesis

    • Make predictions

    • Test predictions by experimentation

    • Analyze and interpret results

    • Conclusions: reject or accept the hypothesis

Hypothesis and Null Hypothesis

  • Hypothesis = educated guess that explains a phenomenon or answers a scientific question

    • Example: If fertilizer runs into a pond, then algae in the pond will change in amount

    • Should be testable and include a prediction

    • Example prediction: Fertilizer running into a pond increases algae

  • Null hypothesis (Ho) = states there is no difference

    • Example: Algae growth in a pond with fertilizer is not significantly different from a control pond

Variables in an Experiment

  • Independent variable ( manipulated variable )

    • Does not change with other variables

    • Example: fertilizer input

  • Dependent variable ( observed variable )

    • Changes with the independent variable

    • Example: quantity of algae

  • Reference for further examples and explanations (Independent vs Dependent Variables):

    • https://www.youtube.com/watch?v=iaewZmc4TYQ

Controls and Constants

  • Experimental group(s)

    • Exposed to the independent variable

    • Produces the dependent variable

    • Usually more than one group

  • Control group

    • Not exposed to the independent variable

    • May not always be necessary or possible

Experimental Design

  • Experiments provide data to determine if the hypothesis should be accepted or rejected

  • Components of an experiment:

    • Treatment: different levels of the independent variable

    • Replications: repeated measurements of each treatment under the same conditions

    • Control: standard for comparisons

Repeatability and Reliability

  • Repeat/Replication

    • One trial is not enough; other factors may affect results

  • Repetition = Reliability

    • Experiments must be repeatable by other scientists and obtain similar results

Hypothesis Evaluation (Algae Experiment Example)

  • Data (illustrative): Fertilizer (L) vs Algae biomass (g)

    • 0 L (control) → 10 g

    • 2 L → 300 g

    • 4 L → 475 g

    • 6 L → 625 g

  • Interpretation

    • Increasing fertilizer levels correlate with higher algae biomass in this dataset

    • This pattern supports the alternative hypothesis (fertilizer increases algae biomass) and suggests rejection of the null hypothesis if differences are significant

    • Note: Statistical testing is required to declare significance formally

Scientific Methods Lab Procedures

  • Lab assignments derive from the document Lab Worksheet – Science Method and Metric System

  • Scenario 1 (lab worksheet): Catfish mortality rate and algal bloom in the fish tank

  • Scenario 2 (lab worksheet): Pig weight and protein meals

Metric System (Overview)

  • Page header: Metric System

  • English-to-metric conversions (examples):

    • Length: 1 yard ≈ 0.9 meters; 3.28 feet ≈ 1 meter

    • Volume: 1 gallon ≈ 3.8 liters

    • Mass: 1 pound ≈ 453.5 grams; 2.2 pounds ≈ 1 kilogram

    • Temperature: 50°F ≈ 10°C; 0°C ≈ 32°F; 37°C ≈ 98.6°F; 25°C ≈ 77°F; 104°F ≈ 40°C

  • Temperature conversion formula (alternative form):

    • 5\,F = 9\,C + 160

    • Equivalent common form: F = \frac{9}{5}C + 32

  • Reference: YouTube video on metric system conversions

Metric System Prefixes

  • Greek prefixes (multipliers):

    • giga (G): 10^9

    • mega (M): 10^6

    • kilo (k): 10^3

    • hecto (h): 10^2

    • deka (da): 10^1

  • Latin prefixes (multipliers or submultipliers):

    • deci (d): 10^{-1}

    • centi (c): 10^{-2}

    • milli (m): 10^{-3}

    • micro (µ): 10^{-6}

    • nano (n): 10^{-9}

    • pico (p): 10^{-12}

Measurement of Length

  • Meter (m) = basic unit of distance/length

  • Units of area are squared units of length (e.g., m²)

Measurement of Volume

  • Volume = space occupied by an object

  • Basic metric unit of volume = liter (L)

  • Common measuring devices:

    • Beaker

    • Erlenmeyer flask

    • Graduated cylinders

    • Pipets

  • Meniscus reading guidance

    • Observe liquid in a graduated cylinder; water forms a meniscus due to surface tension and adhesion

    • When measuring liquids, read at eye level with the meniscus

    • Read the volume at the lowest/middle point of the curve

  • Example discussion: What is the correct volume? 36, 35, or 39 mL? (Check the bottom of the meniscus)

  • Pipetting technique: watch the recommended pipetting method video

Measurement of Mass

  • The gram (g) is the basic unit of mass in the metric system

  • Instruments: triple-beam balance

  • Components on a triple-beam balance include adjustment knob, movable masses, and pan

Measurements of Temperature

  • Biologists measure temperature in degrees Celsius (°C)

  • Common conversions include:

    • 100^{\circ}C = 212^{\circ}F

    • 0^{\circ}C = 32^{\circ}F

    • 37^{\circ}C = 98.6^{\circ}F

  • Practice conversions using the formula provided above

Understanding Numerical Data and Statistics

  • Statistics = method to organize, summarize, and describe data

  • Mean (average)

    • Definition: \bar{x} = \frac{\sum{i=1}^n xi}{n}

    • Example dataset: 1, 1, 1, 2, 2, 4, 5, 5, 6, 8, 10

    • Mean = 4.1

  • Median

    • Definition: middle value in an ordered data set

    • Example: for the same dataset, Median = 4

  • Range

    • Definition: difference between the highest and lowest values

    • Example: Range = x{\max} - x{\min} = 9 in the example dataset

  • Standard Deviation (SD)

    • Definition: positive square root of the variance

    • Population SD ((\sigma)) example (conceptual):

    • \sigma = \sqrt{ \frac{1}{N} \sum{i=1}^N (xi - \mu)^2 }

    • Sample SD ((s)) example (conceptual):

    • s = \sqrt{ \frac{1}{n-1} \sum{i=1}^n (xi - \bar{x})^2 }

  • Additional resources

    • Calculating Numerical Data: https://www.youtube.com/watch?v=mk8tOD0t8M0

Quick Reference: Links and Resources

  • YouTube references for additional explanations:

    • Independent vs. Dependent Variables: https://www.youtube.com/watch?v=iaewZmc4TYQ

    • Metric System overview: https://www.youtube.com/watch?v=k6Nkv1mJEoM

    • Pipetting techniques: https://www.youtube.com/watch?v=uEyNGDfo8