Experimental Design

Independent Variable the variable that is changed on purpose the cause, stimulus, manipulated variable This is the ‘’if” part of a hypothesis and is graphed on the “x” axis.

Dependent Variable the variable that responds The effect(s), result(s), responding variable, etc. This is the ‘’then” part of a hypothesis and is graphed on the “Y” axis.

The dependent variable can be: Quantitative Data Specific, numerical measurements Use metric system units (cm, ml, gram, ◦C) Qualitative Data Descriptive, non- numerical Ex: Color, shape, texture, smell

Constants Do not change (items to set up the lab) Must have at least five constants always…..

Control Group contains NO variable, only constants Dependent Variable results are compared to this group

the group(s) being tested contain the independent variable Experimental Group the group(s) being tested contain the independent variable only one factor is changed

Repeated Trials number of repetitions Increases validity

to design an experiment. The IVCDV chart is used to design an experiment. Research: Redi Spallanzani Pasteur

Alka Seltzer Lab

Does the amount of water affect Alka Seltzer? Measure 100 ml of water (use beaker). Determine the temperature of the water to the nearest tenth of a ºC. Add one tablet. Determine the temperature at the end of the reaction. Repeat, but this time use 50 ml of water.

The independent variable is changed IV Constants DV Amount of Water The independent variable is changed

The measurable results …the dependent variable. IV Constants DV Temperature change Amount of water The measurable results …the dependent variable.

Factors that remain the same. IV Constants DV Amount of water container Temperature change Amount of alka seltzer Time Factors that remain the same. How fast

forming a hypothesis

If the amount of water is increased iv constants container Amount of alka seltzer Time Themometer Light Room Temeperature dv Amount of water Temperature change + verb + verb If the amount of water is increased then the change in temperature will decrease because……………….……………………………..

Hypothesis or claim of experiment Must connect independent variable to dependent variable and justify the outcome.

Extension: What other factors could affect results?