Lab 1 Objectives
• Name the kingdom and phylum to which planarians belong
• Planarians – type of flatworm
• Kingdom: Animalia
• Phylum: Platyhelminthes
• Explain basic anatomical and physiological features of planarians
• Gastrovascular cavity with only ONE opening
• Extendable pharynx
• Eyespots and chemoreceptors on anterior
• Capable of asexual AND sexual reproduction
• Formulate a good null hypothesis, following all rules
Null hypothesis rules:
1. It is a statement, not a prediction. It is in the present tense.
2. It is a generalization. It applies to people in general, or flatworms in general, or slime molds
in general, etc. It does not mention results (data).
3. It is never a prediction of results.
4. It is based on the idea that nothing unusual is taking place. It usually involves two population
averages being the same or a certain proportion holding true. It is usually the opposite of what
you are hoping to prove.
• Apply the terms independent variable, dependent variable, treatments, and replicates to
your experiment
• Treatment variable: same as independent variable
• replicates to your experiment: Getting the same result when an experiment is
repeated is called replication. If research results can be replicated, it means they
are more likely to be correct. Replication is important in science so scientists
can “check their work.
• independent variable: variable whose change isn’t affected by any other variable
in the experiment; example: age and time
• dependent variable: what is being studied and measured in the experiment.
• the independent variable is what you change, and
the dependent variable is what changes because of
that. You can also think of the independent variable as the cause
and the dependent variable as the effect.
• Explain the purpose of a chi-square analysis
• intended to test how likely it is that an observed distribution is due to chance. It is
also called a "goodness of fit" statistic, because it measures how well the observed
, distribution of data fits with the distribution that is expected if the variables are
independent; categorical/ nominal
• Calculate a chi-square
• Interpret the results of a chi-square analysis using a table of critical values
A very small chi square test statistic means that your observed data fits your expected data
extremely well. ... A very large chi square test statistic means that the data does not fit very
well.
• Determine your p value and explain it in terms of probability
The P-value is the probability that a chi-square statistic having 2 degrees of freedom is more
extreme than 19.58. We use the Chi-Square Distribution Calculator to find P(Χ2 >
19.58) = 0.0001. Interpret results. Since the P-value (0.0001) is less than the
significance level (0.05), we cannot accept the null hypothesis.
• Name the kingdom and phylum to which planarians belong
• Planarians – type of flatworm
• Kingdom: Animalia
• Phylum: Platyhelminthes
• Explain basic anatomical and physiological features of planarians
• Gastrovascular cavity with only ONE opening
• Extendable pharynx
• Eyespots and chemoreceptors on anterior
• Capable of asexual AND sexual reproduction
• Formulate a good null hypothesis, following all rules
Null hypothesis rules:
1. It is a statement, not a prediction. It is in the present tense.
2. It is a generalization. It applies to people in general, or flatworms in general, or slime molds
in general, etc. It does not mention results (data).
3. It is never a prediction of results.
4. It is based on the idea that nothing unusual is taking place. It usually involves two population
averages being the same or a certain proportion holding true. It is usually the opposite of what
you are hoping to prove.
• Apply the terms independent variable, dependent variable, treatments, and replicates to
your experiment
• Treatment variable: same as independent variable
• replicates to your experiment: Getting the same result when an experiment is
repeated is called replication. If research results can be replicated, it means they
are more likely to be correct. Replication is important in science so scientists
can “check their work.
• independent variable: variable whose change isn’t affected by any other variable
in the experiment; example: age and time
• dependent variable: what is being studied and measured in the experiment.
• the independent variable is what you change, and
the dependent variable is what changes because of
that. You can also think of the independent variable as the cause
and the dependent variable as the effect.
• Explain the purpose of a chi-square analysis
• intended to test how likely it is that an observed distribution is due to chance. It is
also called a "goodness of fit" statistic, because it measures how well the observed
, distribution of data fits with the distribution that is expected if the variables are
independent; categorical/ nominal
• Calculate a chi-square
• Interpret the results of a chi-square analysis using a table of critical values
A very small chi square test statistic means that your observed data fits your expected data
extremely well. ... A very large chi square test statistic means that the data does not fit very
well.
• Determine your p value and explain it in terms of probability
The P-value is the probability that a chi-square statistic having 2 degrees of freedom is more
extreme than 19.58. We use the Chi-Square Distribution Calculator to find P(Χ2 >
19.58) = 0.0001. Interpret results. Since the P-value (0.0001) is less than the
significance level (0.05), we cannot accept the null hypothesis.
