Experimental Design Independent Variable the variable that is

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, nonnumerical • 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

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

Repeated Trials number of repetitions Increases validity

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

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.

IV Amount of Water Constants DV The independent variable is changed

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

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

forming a

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

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

Extension: What other factors could affect results?