18 lines
753 B
Python
18 lines
753 B
Python
from lib.irt.models.three_parameter_logistic import ThreeParameterLogistic
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class ItemInformationFunction():
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def __init__(self, irt_model):
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self.model_data = irt_model
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# determines the amount of information for a given question at a given theta (ability level)
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# further detailed on page 161, equation 4 here:
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# https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5978482/pdf/10.1177_0146621615613308.pdf
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def calculate(self, **kwargs):
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if self.model_data.model == '3PL':
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p = ThreeParameterLogistic(self.model_data, kwargs).result()
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q = 1 - p
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return self.model_data.a_param**2 * ((q / p) * ((p - (self.model_data.c_param**2)) / (1 - (self.model_data.c_param**2))))
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else:
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# potentially error out
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return None
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