Standard LS.1
Investigations

Standard LS.1
The student will plan and conduct investigations in which
a) data are organized into tables showing repeated trials and means;
b) variables are defined;
c) metric units (SI — International System of Units) are used;
d) models are constructed to illustrate and explain phenomena;
e) sources of experimental error are identified;
f) dependent variables, independent variables, and constants are identified;
g) variables are controlled to test hypotheses, and trials are repeated;
h) continuous line graphs are constructed, interpreted, and used to make predictions;
i) interpretations from a set of data are evaluated and defended; and
j) an understanding of the nature of science is developed and reinforced.

KEY CONCEPTS

• Expected results are reflected in the organization of the data table, which includes areas to record the number of repeated trials, levels of the independent variable, measured results for the dependent variable, and analysis of the results by calculation of the means.
• Systematic investigations require a hypothesis stated in such a way that it identifies the independent variable (parameter that is deliberately changed), the dependent variable (the response that can be measured or observed because of changes in the independent variable), and the relationship between them.
• Investigations will use International System of Units (metric units) of measurement.
• Mental and physical models can be helpful in explaining events or sequences of events that occur. They can be used as part of scientific explanations to support data or represent phenomena, especially those that are not easily seen directly or must be inferred from data.
• Potential sources of error in the experimental design must be identified.
• To communicate the plan of an experiment accurately, the independent variable, dependent variable, and constants must be explicitly defined.
 
• To establish that the events of an experiment are the result of manipulating the independent variable, the experiment must be controlled by observing the effects without the application of the independent variable. The results can be compared with this standard or control. Not all experiments have a control.
• Multiple trials of an experiment must be conducted to verify the results.
• Analysis of observed results of systematic investigations includes construction and interpretation of graphs. Such interpretation can be used to make predictions about the behavior of the dependent variable in other situations and to explore potential sources of error in the experiment. This analysis can be used to support conclusions about the results of the investigation.
• Investigations can be classified as observational (descriptive) studies (intended to generate hypotheses), or experimental studies (intended to test hypotheses).
• Experimental studies sometimes follow a sequence of steps known as the Scientific Method: stating the problem, forming a hypothesis, testing the hypothesis, recording and analyzing data, stating a conclusion. However, there is no single scientific method. Science requires different abilities and procedures depending on such factors as the field of study and type of investigation.
KNOWLEDGE AND SKILLS
• design a data table that includes space to organize all components of an investigation in a meaningful way, including levels of the independent variable, measured responses of the dependent variable, number of trials, and mathematical means.
• identify what is deliberately changed in the experiment and what is to be measured as the dependent (responding) variable.
• select appropriate tools for collecting qualitative and quantitative data and record measurements (volume, mass, and distance) in metric units..
• create physical and mental models as ways to visualize explanations of ideas and phenomena.
• evaluate the design of an experiment and the events that occur during an investigation to determine which factors may affect the results of the experiment. This requires students to examine the experimental procedure and decide where or if they have made mistakes.
• analyze the variables in an experiment and decide which ones must be held constant (not allowed to change) in order for the investigation to represent a fair test. This requires students to comprehend what “variables” are and to apply that idea in new situations related to the Life Science SOL concepts.
• determine the specific component of an experiment to be changed as an independent variable and control the experiment by conducting trials for the experiment in which the independent variable is not applied. This requires the student to set up a standard to which the experimental results can be compared. The student must use the results of the controlled trials to determine whether the hypothesized results were indeed due to the independent variable.
• construct appropriate graphs, using data sets from experiments. This requires the student to recognize that a line graph is most appropriate for reporting continuous or real-time data. This also requires a student to comprehend that points along the line that are not actual data points can be used to make predictions. Students should be able to interpret and analyze these graphs.
• develop conclusions based on a data set and verify whether the data set truly supports the conclusion. This requires students to cite references to the data that specifically support their conclusions.
• distinguish between observational and experimental investigations.
• identify, describe, and apply the generalized steps of experimental (scientific) methodology.