fix IRT formula in 4PL

nd-ball · Dec 16, 2024 · da7fbb5 · da7fbb5
1 parent 4b43b91
commit da7fbb5
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/py_irt/models/four_param_logistic.py b/py_irt/models/four_param_logistic.py
@@ -118,7 +118,7 @@ def model_hierarchical(self, subjects, items, obs):
             disc = pyro.sample("gamma", dist.Normal(mu_gamma, 1.0 / u_gamma))
 
         with pyro.plate("observe_data", obs.size(0)):
-            p_star = torch.sigmoid(disc[items] * (ability[subjects] - diff[items]))
+            p_star = torch.sigmoid(- disc[items] * (ability[subjects] - diff[items]))
             pyro.sample(
                 "obs",
                 dist.Bernoulli(probs=lambdas[items] * p_star),

diff --git a/py_irt/models/tutorial_model.py b/py_irt/models/tutorial_model.py
@@ -122,7 +122,7 @@ def model_hierarchical(self, subjects, items, obs):
             disc = pyro.sample("gamma", dist.LogNormal(mu_gamma, 1.0 / u_gamma))
 
         with pyro.plate("observe_data", obs.size(0)):
-            p_star = torch.sigmoid(disc[items] * (ability[subjects] - diff[items]))
+            p_star = torch.sigmoid(- disc[items] * (ability[subjects] - diff[items]))
             pyro.sample(
                 "obs",
                 dist.Bernoulli(probs=p_star),