Lecture 6 Testing and importance of hypotheses, small and large examplespdf.pdf

Dent 4407 Research Methods in Dentistry Associate Professor Banu Öter, DDS,PhD Bahçeşehir University School of Dentistry Department of Pediatric Dentistry Course Resources Research Ethics 24.10.2023 Assoc Prof Banu Öter Lecture 6: Testing and importance of hypothesis small and large examples...

Dent 4407 Research Methods in Dentistry Associate Professor Banu Öter, DDS,PhD Bahçeşehir University School of Dentistry Department of Pediatric Dentistry Course Resources Research Ethics 24.10.2023 Assoc Prof Banu Öter Lecture 6: Testing and importance of hypothesis small and large examples 7.11.2023 Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Investigation In a research you have to investigate a question … For example, your patients report increased halitosis and a decrease in toothbrushing frequency in 2020. You are looking to find the reasons for this, and you ask the question, “what is the reason for changing oral hygiene habits in 2020 compared to the previous years?” The first and foremost answer to this question is the research hypothesis, for example, “the use of face masks during the COVID-19 pandemic impacts on oral hygiene habits and oral conditions”. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Testing and importance of hypothesis small and large examples In the last step of the investigation phase, the research question must be translated into the hypothesis, and the researcher must imagine the anticipated answers to the question. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Testing and importance of hypothesis Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter The purpose of hypothesis The purpose of hypothesis testing is to test whether the null hypothesis (there is no difference, no effect) can be rejected or approved. If the null hypothesis is rejected, then the research hypothesis can be accepted. If the null hypothesis is accepted, then the research hypothesis is rejected. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter What is hypothesis testing ? Hypothesis testing, sometimes called significance testing, is an act in statistics whereby an analyst tests an assumption regarding a population parameter. The methodology employed by the analyst depends on the nature of the data used and the reason for the analysis. Hypothesis testing refers to a process used by analysts to assess the plausibility of a hypothesis by using sample data. In hypothesis testing, statisticians formulate two hypotheses: the null hypothesis and the alternative hypothesis. A null hypothesis determines there is no difference between two groups or conditions, while the alternative hypothesis determines that there is a difference. Researchers evaluate the statistical significance of the test based on the probability that the null hypothesis is true. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Null hypothesis The null hypothesis is usually a hypothesis of equality between population parameters; e.g., a null hypothesis may state that the population mean return is equal to zero. The alternative hypothesis is effectively the opposite of a null hypothesis (e.g., the population mean return is not equal to zero). Thus, they are mutually exclusive, and only one can be true. However, one of the two hypotheses will always be true. The null hypothesis is a statement about a population parameter, such as the population mean, that is assumed to be true. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter What are the four steps in hypothesis testing ? All hypotheses are tested using a four-step process: The first step is for the analyst to state the hypotheses. The second step is to formulate an analysis plan, which outlines how the data will be evaluated. The third step is to carry out the plan and analyze the sample data. The final step is to analyze the results and either reject the null hypothesis, or state that the null hypothesis is plausible, given the data. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Dependable knowledge As we mentioned before, the hypothesis is a statement that predicts the response to the research question or a provisional declaration of the expected relationships between two or more variables. What will be the supposed behavior of a dependent variable after manipulation of the independent variable? It is the anticipated answer to the research question posed. Before performing the research, you will develop a prediction about the outcome of your study based on the logic of the problem. Then, by conducting experiments and collecting and analyzing data through research, you will test this hypothesis to see if your prediction is accurate or not. As Fred Kerlinger said, “hypothesis is perhaps the most powerful tool man has invented to achieve dependable knowledge.” Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter The objective of a hypothesis The objective of a hypothesis is to provide a framework for answering the research question through statistical tests. The value of scientific work depends heavily on the formulated hypothesis. If a researcher has enough knowledge, he/she can make predictions by formulating hypotheses. It should be emphasized that hypotheses should not be lightly conjectured but must reflect the investigator’s essential knowledge, imagination, and experience. In other words, the observation of “what already exists” and the literature analysis is the basis for developing the hypothesis. Its formulation must be precise so that the main objective of the project meets the identified problem. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Formulating a hypothesis The hypothesis statement makes it possible to present the reasons or rationale for the experiment. The factors to be considered for formulating the hypotheses are: • The statement of relations: In most hypotheses, two main concepts are considered: causes or factors (independent variables) that affect dependent variables. The hypothesis expresses the expected relationship (association) between variables (independent and dependent variables) or the difference between groups Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter The factors to be considers for formulating a hypothesis The relation between two variables can be causal (cause and effect, e.g., “this causes that,” “this explains that,” “this has an impact on that”) or associative (e.g., “this has a connection with that,” “this is related to that”). In a relationship between two variables, the variable to be explained is the dependent variable that you want to measure as your outcome. The explanatory factor is the independent variable that you want to change. The definition of the variable thus depends on the hypothesis specified in the study; a variable may be independent for one hypothesis, may be confusing for another, and may be dependent for a third hypothesis. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Formulating a hypothesis For example, if your hypothesis is about “the relationship between smoking and periodontal disease”, smoking will be the independent variable. However, if the hypothesis is about “the effect of exercise on smoking,” smoking is the dependent variable. On the other hand, smoking could be a confounding variable in the “association between diabetes and periodontal disease”. • If you specify the direction of the difference between groups in your expected outcome by terms such as “less than,” “greater than,” “positive,” and “negative,” you have a one-sided hypothesis. However, in a two-sided hypothesis, which is preferable, there is no specification about the expected direction of the difference. In this case, the meaning of the relation is indicated by terms such as “different from.” Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Testing and importance of hypothesis small and large examples • Verifability: The essence of a hypothesis is that it can be verified. It contains observable variables which can be measured and analyzed. Increasing the number of variables would increase the time required for data collection and complicate the study and the data analysis. • Relevance: The hypothesis must be relevant to the phenomenon under study. In scientific research, depending on the nature of the study and its specific aims, the number of hypotheses may be one or more. We can have a central hypothesis and secondary hypotheses. The number of hypotheses is not imperative, but their coherence and coordination are essential. Secondary hypotheses must be articulated around the central one and call each other in a logic imposed by the research problem. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Testing and importance of hypothesis small and large examples When you formulate a research question based on the PICO (Patient/Population, Intervention, Comparison, Outcomes) framework elements, you can quickly acquire your hypothesis by changing it into a statement; by adding “not,” you can then turn it into a null hypothesis (H0). During the research process, the researcher’s hypothetical answers to the research questions (H0) are accepted or rejected (or the state of uncertainty remains unresolved, especially when the sample size is too small to ensure reliability). We can refuse the null hypothesis when the study results are statistically significant (a statistically significant difference between the variables). Answering a research question can lead to the emergence of a new question, constructing another null hypothesis, and continuity of the research. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Example 1: Consider the following example: • Research question: In endodontic retreatment of patients with peri-radicular lesions, does photodynamic therapy in comparison to the 810 nm diode laser lead to a more or less reduction in the number of microbial fora of the root canal? Variables: Photodynamic therapy and diode laser are independent variables, and the number of the microbial fora of the root canal is the dependent variable. • Hypothesis: – Directional or one-sided: In endodontic retreatment of patients with periradicular lesions, photodynamic therapy leads to a more signifcant reduction in the number of the microbial fora of the root canal than the 810 nm diode laser. – Nondirectional or two-sided: In endodontic retreatment of patients with periradicular lesions, there is a difference between photodynamic therapy and the 810 nm diode laser in reducing the number of the microbial fora of the root canal. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Example 1: Consider the following example: • Research question: In endodontic retreatment of patients with peri-radicular lesions, does photodynamic therapy in comparison to the 810 nm diode laser lead to a more or less reduction in the number of microbial fora of the root canal? • Null hypothesis: In endodontic retreatment in patients with peri-radicular lesions, no difference exists between photodynamic therapy and the 810 nm diode laser in the number of the microbial fora of the root canal. • The following null hypothesis after rejecting the frst one: Different application times of photodynamic therapy have the same effect on reducing the number of the microbial fora of the root canal. • Another null hypothesis: Maximum effect on reduction in the number of the microbial fora of the root canal cannot be achieved after 40 seconds of photodynamic therapy. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Example 2: In an example of maxillofacial trauma you may consider the following research question and hypothesis: • Research question: In multi-tissue loss, including bone and oral mucosa, can we adopt a new method of adhesion with suitable bonding strength that is biocompatible? • Variables: Biocompatibility and bonding strength are dependent variables, and the adhesion method is the independent variable. • Null hypothesis: In multi-tissue loss, including bone and oral mucosa, our new adhesion method is not different from the traditional method regarding bonding strength and biocompatibility. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Benefits of hypothesis testing ? Hypothesis testing helps assess the accuracy of new ideas or theories by testing them against data. This allows researchers to determine whether the evidence supports their hypothesis, helping to avoid false claims and conclusions. Hypothesis testing also provides a framework for decision-making based on data rather than personal opinions or biases. By relying on statistical analysis, hypothesis testing helps to reduce the effects of chance and confounding variables, providing a robust framework for making informed conclusions. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Limitations of hypothesis testing ? Hypothesis testing relies exclusively on data and doesn’t provide a comprehensive understanding of the subject being studied. Additionally, the accuracy of the results depends on the quality of the available data and the statistical methods used. Inaccurate data or inappropriate hypothesis formulation may lead to incorrect conclusions or failed tests. Hypothesis testing can also lead to errors, such as analysts either accepting or rejecting a null hypothesis when they shouldn’t have. These errors may result in false conclusions or missed opportunities to identify significant patterns or relationships in the data. Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter Keep in mind Keep in mind that sometimes when you are researching and synthesizing an entirely new substance, you may not have a hypothesis about the properties of that substance. The hypotheses are written in complete sentences and have a logical connection with the main research question and expression of the problem. The most important features of a reasonable hypothesis are: • Clear, explicit, understandable, and feasible • Specifed before conducting the research • A guide for the researcher that identifes the objectives and shows the general direction for conducting the research • Consistent with existing knowledge: not against the facts and scientifc principles of a feld of knowledge • Leads to the construction of a new hypothesis and further investigation Testing and importance of hypothesis 07.11.2023 Assoc Prof Banu Öter