How to Write a Descriptive Methods Section

Step 1 Organize the steps into small, discrete directions in the order you would do them in the lab. Good Bad 1. Wake up. 1. Get up. 2. Put your feet on the floor. 2. Get out of bed. 3. Stand up.

Step 2 Avoid using pronouns Good: “Place the beaker on the table.” Bad: “Place it on the table.”

Step 3 Use commands Good: “Measure 50 mL of water.” Bad: “50 mL of water.”

Step 4 Eliminate extra information Good: “Measure 50 mL of water.” Bad: “Measure 50 mL of good, clean, fresh, great-tastin’ water!”

Step 5 If applicable, sketch and label the experimental set-up. It does NOT have to cover each step.

Step 6 Include all step. No matter how small the step seems, it may be the critical step for a researcher to replicate the procedure. Ex: Place the beaker on the hot plate. Record the change in water temperature every 5 minutes.

Practice Research Topic: Popcorn Use the Four Question Strategy to design an experiment.

Analyzing Experimental Data

Types of Data Quantitative Data: represented by a number and a unit of measurement that is based upon a standard scale with equal intervals, such as the Metric system Ex: height of a person in meters, mass of a rabbit in kilograms Continuous data: collected using standard measurement scales that are divisible into partial units Ex: distance in kilometers, volume in liters Discrete data: collected using standard scales in which only whole integers are used Ex: number of wolves born in a given year, number of people that can touch their toes

Types of Data Quantitative Ratio Data: quantitative data are collected using a standard scale with equal divisible intervals and an absolute zero Ex: temperature of a gas on the Kelvin scale, velocity of an object in m/sec, distance from a point in meters Interval Data: the scales does not have an absolute zero Ex: temperature of a substance on the Celsius scale

Types of Data Qualitative Data: categorized into 2 categories Discrete: represented by a word or “number” label or measurements made with a nonstandard scale with unequal intervals; reflect a synthesis of many observations made during experimentation Nominal data: exists when objects have been named or placed into discrete categories that cannot be rank ordered Ex: gender, color of hair Ordinal data: exists when objects are placed into categories that can be rank ordered Ex: activity of an animal on a scale of 1 – 5.

Heights of Plants Health of Plants Leaf Quality Practice Classify the three dependent variables in Mary’s experiment as quantitative or qualitative data Heights of Plants Health of Plants Leaf Quality

Heights of Plants Health of Plants Leaf Quality Practice Classify the three dependent variables in Mary’s experiment as quantitative or qualitative data Heights of Plants Health of Plants Leaf Quality Quantitative (continuous) Qualitative Qualitative Ratio (equal intervals, ab. 0) Nominal (discrete cats., Ordinal (discrete cats., ranked) not ranked)

Describing Data Measure of central tendency: the one number that is most typical of the entire set of data Mode: the value of the variable that occurs most often; used for data at the nominal, ordinal, interval, or ratio levels Median: the middle value, after all of the cases have been rank ordered from highest to lowest; can be used with ordinal, interval, or ratio data Mean: the arithmetic average or the sum of the individual values divided by the number of cases; can only be calculated for interval or ratio data

Describing Data Variation: spread within the data Range: computed by finding the difference between the smallest (minimum) and the largest (maximum) measure of the dependent variable Ex: plant height Frequency distribution: depicts the number of cases falling into each category of the variable Ex: the color of tomatoes produced with different fertilizers

Height of Plants Health of Plants Leaf Quality Practice Determine the most appropriate measures of central tendency and variation to calculate for each of the dependent variables in Mary’s experiment: Height of Plants Health of Plants Leaf Quality

Height of Plants Health of Plants Leaf Quality Practice Determine the most appropriate measures of central tendency and variation to calculate for each of the dependent variables in Mary’s experiment: Height of Plants Health of Plants Leaf Quality Mean, Range Mode, Freq. Dist. Median, Freq. Dist.