Scientific Method Tutorial Honors Biology 2014

The Scientific Method: a way to investigate the natural world Observations: examples Inferences: logical explanation which lead to… Hypothesis: must be testable and falsifiable Controlled Experiments: Variables Data: qualitative and quantitative Conclusions: hypothesis supported or refuted Publish and peer review

Observations The act of noticing and describing in an orderly fashion. The senses are used. – There is steam rising from the coffee cup. – I can hear the sound of an organ coming from the church.

Inferences A logical interpretation based on what is known. – From the observation: Steam is rising from the coffee cup you can infer…the coffee is hot. – From the observation: the sound of an organ can be heard you can infer… there is a mass going on in the chapel Inferences can lead to a hypothesis

Hypothesis A scientific explanation for a set of observations that can be tested in a way that can be supported or rejected.

Controlled experiment An experiment in which only one variable is changed, all others are kept the same or controlled.

Controlled experiments Variables Independent variable: the variable that is deliberately changed Dependent variable: the variable that is observed and that changes in response to the independent variable All other variables remain the same or controlled

Control and Experimental Groups A control group is exposed to the same conditions as the experimental groups except for the independent variable

Example Scientists notice that grass in a marsh grows taller in some places than others. This is an observation. The scientists may infer there is a difference in nutrients available to the grass. – an important nutrient for grass is nitrogen.

Example A hypothesis is proposed: Write a hypothesis in If…then because format. If….(I do this)_________ then…. (This will happen)_______because… I know _______________. If the amount of Nitrogen (independent variable) marsh grass receives is increased then the marsh grass will grow taller (dependent variable) because nitrogen is an important nutrient required for growth of grass.

Example The controlled experiment. Everything in the control group is the same as the experimental group except for adding nitrogen (independent variable)

Example Data is collected – There are two types of data Qualitative: data which is descriptive but does not measure characteristics using numbers Quantitative data: information that can be recorded as numbers The height of the grass (dependent variable) is measured: quantitative data

Conclusions Conclusions are drawn based on the data collected. You ask has the data supported or refuted the original hypothesis. If your hypothesis is not supported you may want to revise and try again

Publish and Peer Review Information is shared at scientific conferences and professional journals.